CE2301 Irrigation Engineering Two Marks Questions With Answers 2014

Anna University, Chennai

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SIXTEEN MARK QUESTIONS

UNIT-1

1) What are the merits and demerits of irrigation? Merits of irrigation:

• Reduced water stress

• Better germination and stands

• Higher plant populations

• More efficient use of fertilizer

• Improved varieties

• Leaching of salts

• Frost protection

• Plant/soil cooling

• Chemical application

• Wind erosion control

Waste disposal

Demerits of irrigation Rising of water table Formation of marshy lands Dampness in weather

2) What are the factors affecting duty?

Soil characteristics Climatic condition Rainfall

Base period

Type of crop

Topography of agricultural land

Method of ploughing Method of irrigation Water tax

3) Briefly explain about irrigation efficiencies?

1.Water conveyance efficiency

2. Water application efficiency

3. Water use efficiency

4. consumptive use efficiency

4) What are the consumptive use of water?

consumptive use of water is defined as the total quantity of water used for the growth of the plantsby transpiration and the amount lost by evaporation. Methods of consumptive use of water:

1.Lysimeter method

2.Field experimental method

3.Soil moisture study

5) Briefly explain about planning and development of irrigation project?

Planning of irrigation project: Availability of irrigation water

Selection of probable site for barrage or dam

Discharge observation for the river Marking of alignment of main canal Marking of G.C.A

Final survey

Preparation of drawings

Office works


UNIT-2

1.Briefly explain about canal irrigation?

Types of canal irrigation:

1.Inundation irrigation

2.Perenniel irrigation a)Direct irrigation system b)storage irrigation system

2.Briefly explain about lift irrigation? Types of lift irrigation:

Lifting of water by man or animal power

Lifting of water by Mechanical power

By man or animal power: Doon

Mote

Swinging basket

Wind lass

Persian wheel

By Mechanical power: Open well

Deep well

Shallow well

3.Briefly explain about surface irrigation? Types of surface irrigation:

Furrow Method

Contour farming method

Flooding method

4.Briefly explain about flooding methods? Flooding methods:

a)Controlled flooding

Free flooding Basin flooding Check flooding Border strips

Zig- zag method b)uncontrolled flooding

5.Briefly explain about sprinkler irrigation methods? Types of sprinkler irrigation:

Perforation on lateral pipes

Fixed nozzles on lateral pipes

Rotating sprinklers


UNIT-3

1. What are types of dams?

Based on Materials: Rigid dam

Non rigid dam

Based on structural behavior: Solid gravity dam

Arch dam

Buttress dam

Embankment dam

2. Briefly explain about types of spillways?

types of spillways: Drop spillway Ogee spillway Syphon spillway

Volute siphon spillway

Trough spillway

Shaft spillway

3. What are the causes of failure of Earthen dam?

1.Hydraulic failure

2.Due to seepage failure

3.Erosion

4.Structural failure

5.sloughing

4. What are types Weirs?

The subsurface flow of water place on important

role for the stability of hydraulic structures like weir or barrage

Types of Weirs: Masonry Weir Rockfill weir Concrete weir

5.What are forces acting on a dam?

Forces acting on a dam:

§ Weight of the dam

§ Water pressure

§ Uplift pressure

§ Seismic force

§ Silt pressure

§ Wave pressure

§ Ice pressure


UNIT-4

1. What is the necessity of river training works?

· Proper protection work should be adopted.

· In rainy season , the flood water may submerged the vast cultivated area by overflowing the tank.

· The erosion of river water may damage the structure .

2. Describe in brief different Stages of river training works?

stages of river training works: Rocky stage

Boulder stage Trough stage Delta stage

3. What are the types of spurs? Types of spurs:

Bamboo spur

Timber spur

Boulder spur

4.State the types of canal falls? Types of canal falls:

Ogee fall Rapid fall Stepped fall Trapezoidal fall

5.Briefly explain about classification of cross drainage works?

classification of cross drainage works: Aqueduct

Super passage

Level crossing


UNIT-5

1.Briefly explain about on-farm-development works?

· Formation of field channels

· Formation of internal irrigation channels

· Field drains

· Drops in field drains

· Crossing on field drains whenever required.

2.What are the types of water losses? Types of water losses:

Absorption losses

Percolation losses Evaporation losses Transpiration losses

3.What is the need for PIM?

Sustained need and the need for accurate and timely information.

Reducing that people themselves are solution

agents for than need and problems.

Cutting down time consuming long methods of survey which give results after considerate time.

4.Briefly explain about factors depending losses? Permeability of water

Depth of water

Velocity of water

Amount of silt

Age of the channel

CE2301 IRRIGATION ENGINEERING Two Marks Questions With Answers 2014

Anna University, Chennai

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CE2301 IRRIGATION ENGINEERING UNIT – 1

INTRODUCTION

1) Define irrigation ?

Irrigation is defined as the science of artificial application of water to the land in accordance with the crop requirements.

2) What are the necessity of irrigation ?

1.inadequate rainfall

2.increasing yield of crops

3.growing perennial crops

4.uneven distribution of rainfall.

3) What are the advantages of irrigation?

1.increase in food production

2.optimum benefits

3.general prosperity

4.afforestation.

4) What are the disadvantages of irrigation?

1.over irrigation may lead to water logging

2.it may reduce cropyield

3.it is expensive and complex.

5) What is arid region?

The area where irrigation is must for agriculture is called arid region.

6) What is semi-arid region?

The area in which inferior crops can be grown without irrigation.

7) What is crop period?

The time period that elapses from the instant of its sowing to the instant of its harvesting is called crop period.

8) What is base period?

The time between the first watering of a crop at the time of its sowing to its last watering before harvesting is called the base period.

9) What is rotation period?

The time interval between two such consecutive watering is called frequency irrigation.

10) Define duty of water?

It is the relationship between the volume of water and the area of crops it matures is called duty of water.

11) Define delta of a crop?

Each crop requires a certain amount of water after a certain fixed interval of time, through its period of growth is called delta of a crop.

12) What are the factors on which duty depends?

1.type of crop

2.climate and seasons

3.useful rainfall

4.type of soil

5.efficiency of cultivation method

13) What are kharif crops?

The kharif crops are rice,bajra,jawar,maize,cotton,tobacco, groundnut,etc.

14) What are rabi crops?

Rabi crops are wheat,barley,gram,linseed,mustard,potatoes,etc

15) Define irrigation efficiency?

It is the efficiency of water output to the water input,and is usually expressed as percentage.

16) What is called effective rainfall?

Precipitation falling during the growing period of a crop that is available to meet the evapo-transpiration needs of the crop, is called effective rainfall.


UNIT – 2

IRRIGATION METHODS

1) List some types of irrigation ?

canal irrigation,lift irrigation,tank irrigation,etc

2) What are the necessity of irrigation ?

1.inadequate rainfall

2.increasing yield of crops

3.growing perennial crops

4.uneven distribution of rainfall.

3) What are the advantages of irrigation?

1.increase in food production

2.optimum benefits

3.general prosperity

4.afforestation.

4) What are the disadvantages of irrigation?

1.over irrigation may lead to water logging

2.it may reduce cropyield

3.it is expensive and complex.

5) What are the types of irrigation?

1.surface irrigation

2.sub-surface irrigation.

6) What are the techniques of water distribution in the farms?

1.free flooding

2.border flooding

3.check flooding

4.basin flooding,furrow irrigation method,drip irrigation method.

7)What are the types of sprinkler system?

1.permanent system

2.semi-permanent system

3.portable system

8)what are the advantages of sprinkler irrigation?

1.land levelling is not required

2.fertilisers can be uniformly applied

3.it is less labour oriented

9) what are the limitation of sprinkler irrigation?

1.initial cost of the system is very high

2.it requires larger electrical power

3.high wind may distort sprinkler pattern

10)define tank irrigation?

It is defined as the storage irrigation scheme,which utilizes the water stored on the upstream side of a smaller earth dam

11)define tank banks?

The earthen bunds,spanning across the steams are called tank bunds or tank banks.

12)what is the other name for drip irrigation?

drip irrigation is also called as trickle

irrigation.

13)what is called sprinkler irrigation system?

water is applied to the soil in the form of a spray through a network of pipes and pumps is called sprinkler irrigation system

14)what is called called borders?

land is divided into a number of strips separated by low levees

called borders.


UNIT-3

1) What is meant by canal escape?

Canal escapes are the safety valves of canals &must be provided at regular intervals depending upon the importance of channel& availability of

suitable

drainage for the disposal of the exposed water.

2) State various kinds of dams.

1.earth dams

2.rock fill dams

3.solid masonry gravity dams

4.hollow " " " "

5.timber dams

6.steel dams

7.arch dams

3). State diff types of spillways.

1.straight drop spillway

2.ogee spillway

3.trough spillway

4.side channel spillway

5.shaft spillway

6.syphon spillway

4). What are the various types of dams?

1.earth dams

2.rockfill dams

3.solid masonry gravity

4.hollow “ “

5.timber dams

6.steel dams

7.arch dams

5)What is weir?

The major part of the water is achieved by a raised crest or a small part is achieved by raising shutters then this barrier is known as weir.

6) What is tank sluices?

it is an opening in the form of culvert under the tank bund and supplying water to the distributory channel.

7) Forces acting on arch dams.

1.water pressure

2.uplift “ “

3.earthquake forces

4.silt pressure

5.wave pressure

6.ice “ “

8) Define sluiceway

Pipe or tunnel provided for the withdrawl of water from the dams is known as sluiceway.

9) What is spillway?

Spillway is a structure constructed at a dam site for disposing the surplus water

from upstream to downstream.

10)Types of earthen dams.

1.homogeneous embankment type

2. zoned “ “ “

3. diaphragm type.

11)Define barrage.

the most of the ponding is done by gates and a smaller of it is done by raised crest then the barrier is known as barrage.

12). What are the modes of failure in gravity

dams?

1. by over turning about the toe

2.by crushing

3.by development of tension

4.by sliding

13) Define diversion headwork.

Any hydraulic structure, which offers water to the offtaking canal, is called diversion headwork.

14) What is gravity dam?

a structure which is designed in such a way that its own weight resist external forces and it is more durable .

15)Define stream line.

it represent the path along which the water flows through the subsoil.at a given point in upstream of hydraulic structure will travel its ownpath &will represented the stream line.

16). Types of aeration tanks.

1.air diffusion

2.mechanical aeration

3.combined “ “

17) Limitations of blighs creep theory.

1. no difference b\w hzl & vtl creep

2.hzl distance b\w pipe line is greater than 2 times the depth 3.no idea about exit gradient

1.what do you mean by canal?


Unit - 4

A canal is an artificial channel, generally trapezoidal in shape constructed on the ground to carry water to the fields either from the river or from a tank or reservoir.

2.What are the types of canals?

Alluvial canal

Non-Alluvial canal

3.What is alignment of canals?

Watershed canal contour canal Side slope canal

4.What is distribution system of canal irrigation?

Main canal Branch canal Minor canal Major canal Water courses

5.Define tank banks?

The earthen bunds, spanning across the steams are called tank bunds or tank banks.

6.What is called alluvial soil?

The process of silt deposition may continue over long periods in the formation is called alluvial soil.

7.What is called Non-alluvial soil?

Mountainous regions may go on disintegrating over a period of time, resulting formation of a rocky plain area called non-alluvial soil.

8.What is called Watershed canal?

The dividing ridge line between the catchment areas of two streams is called

Watershed canal.

9.List out the alignment of a fields canal?

They should be laid along field boundaries.

They should be capable of supplying sufficient water to tail

Separate field channels should be provided for high and low lands.

10.Define cross drainage works?

cross drainage work or drainage crossing is a structure constructed to negotiate an irrigation canal over, below or at the same level of drainage or another canal.

11.Define aqueduct and Write the different types of Aqueduct?

Aqueduct is defined as the a drainage crossing in which the canal is carried over the drainage channel and the bottom at the canal trough or the covering over the drainage opening is above the high floods level in the drainage channel.

Types of Aqueduct:

Barrel type Aqueduct Arch type Aqueduct Trough type Aqueduct Buttress Aqueduct

12.Define syphon aqueduct and the types of syphon aqueduct? Syphon Aqueduct:

It is defined as a drainage crossing in which the canal is carried over the drainage channel preferably at right angle of the drainage discharge is carried under pressure through the structure.

Types of Syphon Aqueduct: Trough type Aqueduct

Barrel type Aqueduct

13.What do you meant by super passage?

It is defined as a drainage crossing in which the drainage channel in a trough over the canal normally with full supply level at the canal below the bottom of the trough.

14.List out the collection at site data?

Index plan Catchment plan Site plan Geological plan Rainfall

Discharge and sediment data The canal & drainage data Seismic disturbances

15.Define canal regulators? Head regulators:

The regulates or control the supplies to the off taking channel. They serve as a meter for measuring discharge entering into the off taking canal.

Cross regulators:

They effective regulation of the whole canal system can be done with the help of cross regulator. It helps in closing the supply to the discharge of the Parent channel.


UNIT -5

IRRIGATION WATER MANAGEMENT

1).what are the causes of water loss?

1. seepage from the canal

2. over irrigation of field

3. heavy surface runoff

2) what are ways of water loss in the canal?

1. seepage loss

2. evaporation loss

3) What are factors on which seepage loss depends?

position of water table porosity of sub-soil porosity of soil

extend of absorbing medium

4) What are two different condition of seepage?

1.percolation

2.absorption

5. What are the remedial measures for losses?

1.efficient surface drainage

2..restriction of irrigation

3.change in crop pattern

6) What are the advantages of irrigation water managements?

1 .achievement of optimum irrigation efficiency

2.economical and efficient operation and maintanence of irrigation system

3.equitable distribution of supplies to irrigators especially at the end

7) Discuss some components of water management?

1.water shed management

2.land management

3.rain water management

4.reservoir management

8.What are the impact of water user association?

1.conveyance efficiency

2.operation efficiency

3.equity

4.area water unit ratio

9.) What are the advantages of water user association?

1.better maintenance of the distributry

2.possibility of high value of crop programme

3.availability of water and irrigation process

10) What are optimization of water user association?

1.to reduce the seepage loss and conveyance

2.control over the usage of water

3.planning

4.to avoid excess supply of water

11).what are the factors which influence evaporation loss?

1.temperature

2.wind velocity

3.relative humidity

12. What is land management?

The intensity of raising productivity per unit area per unit time needs to be increased which amounts to increasing croped area.

13. What are the irrigation methods for cultivation?

1.border strip-wheat

2.furrow method –cotton

3.basin method –orchard

14. What are the uses of irrigation waters?

1.wastages due to over irrigation

2.wastages due to surface runoff

3.wastages due to escape of water

15. What are the work of on farm development?

1.irrigation practice

2.crop planning

3.irrigation method

4.right amount of irrigation

16. what are the components of on farm developments?

1.field drain

2.crossing in field channel

3.crossing of field channel

4.formation of field channel

17. What is called optimum water depth?

The quantity of water at which the yield is maximum, is called the

optimum water depth.

18. What is called optimum utilisation of irrigation?

It generally means, getting maximum yield with any amount of

water.

19.what is the relation between efficieny and losses?

efficieny is inversely proportional to the losses.

ME 6301- ENGINEERING THERMODYNAMICS Two Marks Questions With Answers 2014

Anna University, Chennai

DEPARTMENT OF MECHANICAL ENGINEERING

ME 6301- ENGINEERING THERMODYNAMICS TWO MARKS QUESTION AND ANSWER

1. Define the term thermal engineering.

Ans: Thermal engineering is the science that deals with the energy transfer to practical

applications such as energy transfer power generation, refrigeration, gas compression and its effect on the properties of working substance.

2. What is meant by thermodynamic system? How do you classify it? (MU – Oct’99, Apr’2000: BRU – Apr’96; MSU – Apr’96)

Ans: Thermodynamic system is defined as the any space or matter or group of matter

where the energy transfer or energy conversions are studied.

It may be classified into three types. (a) Open system

(b) Closed system

(c) Isolated system

3. What is meant by closed system? Give an example.(BNU – Nov’95)

Ans: When a system has only heat and work transfer, but there is no mass transfer, it is

called as closed system.

Example: Piston and cylinder arrangement.

4. Define a open system, Give an example.

Ans: When a system has both mass and energy transfer it is called as open system.

Example: Air Compressor.

5. Differentiate closed and open system. (MU – Apr’98, MKU – Nov’95)

Closed System

Open System

1. There is no mass transfer. Only heat and

work will transfer.

1. Mass transfer will take place, in addition

to the heat and work transfer.

2. System boundary is fixed one

2. System boundary may or may not

change.

3. Ex: Piston & cylinder arrangement,

Thermal power plant

3. Air compressor, boiler

6. Define an isolated system

Ans: Isolated system is not affected by surroundings. There is no heat, work and mass

transfer take place. In this system total energy remains constant. Example: Entire Universe

7. Define: Specific heat capacity at constant pressure. (MU – Oct’99)

Ans: It isdefined as the amount of heat energy required to raise or lower the temperature

of unit mass of the substance through one degree when the pressure kept constant. It is denoted by Cp.

8. Define: Specific heat capacity at constant volume.

Ans: it is defined as the amount of heat energy required to raise or lower the temperature

of unit mass of the substance through one degree when volume kept constant.

9. What is meant by surroundings?

Ans: Any other matter out side the system boundary is called as surroundings.

10. What is boundary?

Ans: System and surroundings are separated by an imaginary line is called boundary.

11. What is meant by thermodynamic property? (MU – Apr’2001; BRU – Nov’96;

BNU – Nov’94)

Ans: Thermodynamic property is any characteristic of a substance which is used to

identify the state of the system and can be measured, when the system remains in an equilibrium state.

12. How do you classify the property?

Ans: Thermodynamic property can be classified into two types.

1. Intensive or Intrinsic and

2. Extensive and Extrinsic property.

13. Define Intensive and Extensive properties. (MU – Oct’96,98; MKU – Apr’96) Ans: The properties which are independent on the mass of the system is called intensive properties.

e.g., Pressure, Temperature, Specific Volume etc.,

The properties which are dependent on the mass of the system is called extensive properties.

e.g., Total energy, Total volume, weight etc.

14. Differentiate Intensive and Extensive properties (MU – Apr’99, Apr’2001; MSU

Intensive Properties

Extensive Properties

1. Independent on the mass of the system

Dependent on the mass of the system.

2. If we consider part of the system these

properties remain same.

e.g. pressure, Temperature specific volume etc.,

If we consider part of the system it will

have a lesser value.

e.g., Total energy, Total volume, weight etc.,

3. Extensive property/mass is known as

intensive property

--

– Nov’96)

15. What do you understand by equilibrium of a system?

Ans: When a system remains in equilibrium state, it should not undergo any charges to its

own accord.

16. What is meant by thermodynamic equilibrium? (MU – Apr’98; MSU – Apr’96) Ans: When a system is in thermodynamic equilibrium, it should satisfy the following three conditions.

(a) Mechanical Equilibrium :- Pressure remains constant (b) Thermal equilibrium :- Temperature remains constant (c) Chemical equilibrium : There is no chemical reaction.

17. State the First law of thermodynamics (MU – Apr’95)

Ans:First of thermodynamics states that when system undergoes a cyclic process the net

heat transfer is equal to work transfer.

18. Define: PMM of first kind

Ans: PMM of first kind delivers work continuously without any input. It violates first

law of thermodynamics, It is impossible to construct an engine working with this principle.

19. Define the term process (MKU – Nov’96)

Ans: It is defined as the change of state undergone by a gas due to energy flow.

20. Define the term Cycle: (MKU – Nov’96)

Ans: When a system undergoes a series of processes and return to its initial condition, it

is known as cycle.

21. What is meant by open and closed cycle.

Ans: In a closed cycle, the same working substance will recirculate again and again.

In a open cycle, the same working substance will be exhausted to the surroundings after expansion.

22. What is meant by reversible and irreversible process. (MU – Apr’2001; BNU – Nov’94)

Ans: A process is said to be reversible, it should trace the same path in the reverse

direction when the process is reversed. It is possible only when the system passes through a continuous series of equilibrium state.

If a system does not pass through continuous equilibrium state, then the process is said to be irreversible.

23. What is meant by Point and Path function? (Mu – Oct’2000; MKU – Nov’94) Ans: The quantities which is independent on the process or path followed by the system is known as point functions.

Example: Pressure, volume, temperature, etc.,

The quantities which are dependent on the process or path followed by the system is known as path functions.

Example: Heat transfer, work transfer.

24. What is Quasi – Static process? (MU – Oct’98, Apr’2000 & 2001; BNU – Nov’95)

Ans: The process is said to be quasi – static, it should proceed infinitesimally slow and

follows continuous series of equilibrium states. Therefore, the quasi static, it should proceed infinitesimally slow and follows continuous series of equilibrium states. Therefore, the quasi static process may be an reversible process.

25. Explain Zeroth Law of thermodynamics? (MU – Nov’94, Apr’2001; BRU – Apr’96)

Ans: Zeroth law of thermodynamics states that when two systems are separately in

thermal equilibrium with a third system, then they themselves are in thermal equilibrium with each other.

26. Define the term enthalpy? (MU – Oct’99)

Ans: The Combination of internal energy and flow energy is known as enthalpy of the

system. It may also be defined as the total heat of the substance. Mathematically, enthalpy (H) = U + pv KJ)

Where, U – internal energy p – pressure

v – volume

In terms of Cp & T → H = mCp (T2-T1)KJ

27. Define the term internal energy (MKU – Apr’96)

Ans: Internal energy of a gas is the energy stored in a gas due to its molecular

interactions.

It is also defined as the energy possessed by a gas at a given temperature.

28. What is meant by thermodynamic work?

Ans: It is the work done by the system when the energy transferred across the boundary

of the system. It is mainly due to intensive property difference between the system and surroundings.

29. Define Heat.

Ans: Heat is the energy crossing the boundary due to the temperature difference between

the system and surroundings.

30. Give the general gas energy equations. (MU – Apr’95 & 98)

Ans: dH = dE + dW.

31. State the law of conservation of energy (BRU – Nov’95)

Ans: Energy can neither be created nor destroyed, but it can be transferred from one form to another.

32. Define entropy of a pure substance. (MU – Oct’2000; MKU – Nov’96; BRU – Nov’95)

Ans: Entropy is an important thermodynamic property, which increases with addition of

heat and decreases with its removal. Entropy is a function of temperature only. It is an unavailability of energy during energy transfer.

33. Define an isentropic process. (MU – Oct’99)

Ans: Isentropic process is also called as reversible adiabatic process. It is a process which follows the law of pVy = C is known as isentropic process. During this process entropy remains constant and no heat enters or leaves the gas.

34. Explain the throttling process.

Ans: When a gas or vapour expands and flows through an aperture of small size, the

process is called as throttling process.

35. Work done in a free expansion process is (MU – Apr’97)

Ans: Zero

36. Define free expansion process.

Ans: When a gas expands suddenly into a vacuum through a large orifice is known as

free expansion process.

37. Which property is constant during throttling? (MU – Oct’98, Oct’2000)

Ans: Enthalpy

38. If in the equation PVn = C, the value of n = then the process is called

Ans: Constant Volume process

39. The polytropic index (n) is given by (MU – Apr’95 & 96)

Ans: n = log (P2/P1)/ log (V1/V2)

40. Work transfer is equal to heat transfer in case of process.MU –Nov’94)

Ans: Isothermal process.

41. Write down the characteristic gas equation. Ans: Characteristic gas equation is pV = mRT Where,

p = pressure

V = Volume

R = Characteristic gas constant

T = Temperature.

42. What is meant by steady flow process? (BNU – Nov’96)

Ans: During the process the rate of flow of mass and energy across the boundary remains constant, is known as steady flow process.

43. What is the difference between steady flow and non – flow process?

Ans: During the steady flow process the rate of flow of mass and energy across the

boundary remains constant.

In case of non – flow across the system and boundary.

44. State the Kelvin – Plank statement of second law of thermodynamics

Ans: Kelvin – Plank states that it is impossible to construct a heat engine working on

cyclic process, whose only purpose is to convert all the heat energy given to it into an equal amount of work.

45. State Clausius statement of second law of thermodynamics.

Ans: It states that heat can flow from hot body to cold without any external aid but heat

cannot flow from cold body to hot body without any external aid.

46. State Carnot’s theorem.

Ans: No heat engine operating in a cyclic process between two fixed temperature, can be

more efficient than a reversible engine operating between the same temperature limits.

47. What are the Corollaries of Carnot theorem.

Ans: (i) In all the reversible engine operating between the two given thermal reservoirs

with fixed temperature, have the same efficiency.

(ii) The efficiency of any reversible heat engine operating between two reservoirs is independent of the nature of the working fluid and depends only on the temperature of the reservoirs.

48. Define – PMM of second kind.

Ans: Perpetual motion machine of second kind draws heat continuously from single

reservoir and converts it into equivalent amount of work. Thus it gives 100% efficiency.

49. What is the difference between a heat pump and a refrigerator?

Ans: Heat pump is a device which operating in cyclic process, maintains the temperature

of a hot body at a temperature higher than the temperature of surroundings.

A refrigerator is a device which operating in a cyclic process, maintains the temperature of a cold body at a temperature lower than the temperature of the surroundings.

50. What is meant by heat engine?

Ans: A heat engine is a device which is used to convert the thermal energy into

mechanical energy.

51. Define the term COP?

Ans: Co-efficient of performance is defined as the ratio of heat extracted or rejected to

work input.

Heat extracted or rejected

COP = -------------------------------- Work input

52. Write the expression for COP of a heat pump and a refrigerator?

Ans: COP of heat pump

 

Heat Supplied

T2

COP HP =

------------------- =

--------

 

Work input

T2-T1

COP of Refrigerator

 

Heat extrated

 

T1

COP HP =

---------------

=

--------

 

Work input

 

T2-T1

53. What is the relation between COPHP and COP ref?

Ans: COPHP = COPref +1

54. Why Carnot cycle cannot be realized in practical?

Ans: (i) In a Carnot cycle all the four process are reversible but in actual practice there is

no process is reversible.

(ii) There are two processes to be carried out during compression and expansion. For isothermal process the piston moves very slowly and for adiabatic process the piston moves as fast as possible. This speed variation during the same stroke of the piston is not possible.

(iii) It is not possible to avoid friction moving parts completely.

55. Name two alternative methods by which the efficiency of a Carnot cycle can be

increased.

Ans: (i) Efficiency can be increased as the higher temperature T2 increases. (ii) Efficiency can be increased as the lower temperature T1 decreases.

56. Why a heat engine cannot have 100% efficiency?

Ans: For all the heat engines there will be a heat loss between system and surroundings.

Therefore we can’t convert all the heat input into useful work.

57. When will be the Carnot cycle efficiency is maximum?

Ans: Carnot cycle efficiency is maximum when the initial temperature is 0°K.

58. What are the processes involved in Carnot cycle.

Ans: Carnot cycle consist of

i) Reversible isothermal compression ii) isentropic compression

iii) reversible isothermal expansion iv) isentropic expansion

59. Write the expression for efficiency of the carnot cycle.

T2 – T1

Ans: n = --------- T2

60. Define: Thermodynamic cycles.

Ans: Thermodynamic cycle is defined as the series of processes performed on the system,

so that the system attains to its original state.

61. Define the term compression ratio.

Ans: Compression ratio is the ratio between total cylinder volume to clearance volume.

It is denoted by the letter ‘r’

62. What is the range of compression ratio for SI and diesel engine?

Ans: For petrol of SI engine 6 to 8

For diesel engine 12 to 18.

63. Which cycle is more efficient for the same compression ratio and heat input, Otto cycle or Diesel cycle?

Ans: Otto cycle is more efficient than diesel cycle

64. Write the expression for efficiency of the otto cycle?

Ans:

1

Efficiency n =1 - --------- (r)r-1

65. The efficiency of the diesel cycle approaches the otto cycle efficiency when the cut off ratio is

Ans: reduced

66. Which device is used to control the Air – fuel ratio in the petrol engine?

Ans: Carburettor

67. Which device is used to control the Air fuel ratio in the diesel engine?

Ans: Injection nozzle

68. The speed of a four stroke I.C. engine is 1500rpm. What will be the speed of the cam shaft?

Ans: 750 rpm.

69. All the four operations in two stroke engine are performed in number of revolution of crank shaft.

Ans: one

70. All the four operations in four stroke engine are performed in number of operations?

Ans: Two

71. In otto cycle the compression ratio is to expansion ratio.

Ans: Equal

clip_image00172. In diesel engine, the compression ratio is

Ans: Greater

than expansion ratio?

73. What is meant by cutoff ratio?

Ans: Cutoff ratio is defined as the ratio of volume after the heat addition to before the

heat addition. It is denoted by the letter ‘p’

74. What are the assumptions made for air standard cycle.

Ans:

1. Air is the working substance.

2. Throughout the cycle, air behaves as a perfect gas and obeys all the gas laws.

3. No chemical reaction takes place in the cylinder

4. Both expansion and compression are strictly isentropic

5. The values of specific heats of the air remain constant throughout the cycle.

75. What is the difference between otto and Diesel cycle.

Otto Cycle

Diesel Cycle

1. Otto cycle consist of two adiabatic and

two constant volume process.

1. It consists of two adiabatic, one constant

volume and one constant pressure processes.

2. Compression ratio is equal to expansion

ratio

2. Compression ratio is greater than

expansion ratio.

3. Heat addition takes place at constant

volume.

3. Heat addition takes place at constant

pressure

4. Compression ratio is less. It is varies

from 6 to 8.

4. Compression ratio is more. It varies

from 12 to 18.

76. What is the other name given to otto cycle?

Ans: Constant volume cycle.

77. What is meant by air standard efficiency of the cycle?

Ans: It is defined as the ratio of work done by the cycle to the heat supplied to the cycle.

Work done

Efficiency n = -------------- Heat supplied

78. Define: Mean effective pressure of an I.C. engine.

Ans: Mean effective pressure is defined as the constant pressure acting on the piston

during the working stroke. It is also defined as the ratio of work done to the stroke volume or piston displacement volume.

79. What will be the effect of compression ratio on efficiency of the diesel cycle?

Ans: Efficiency increases with the increase in compression ratio and vice – versa.

80. What will be the effect of cut off ratio on efficiency of the diesel cycle.

Ans: Efficiency decreases with the increase of cut off ratio and vice – versa.

81. The thermal efficiency of a two stroke cycle engine is than the four stroke cycle engine.

Ans: Lesser.

82. Define: Specific fuel consumption.

Ans: SFC is defined as the amount of fuel consumed per brake power hour of work.

83. What is meant by calorific value of a fuel.

Ans: Calorific value of a fuel is defined as the amount of heat liberated by the compete

combustion of unit quantity of a fuel.

84. Give the expression for efficiency of the Dual cycle.

Ans:

where,

1 Kpr - 1

Efficiency n = 1 - ------- ----------------- (r)r-1 (K-1) + yK(p-1)

r – Compression ratio

k – pressure or Expassion ratio p – cut off ratio and

y – adiabatic index

85. The efficiency of the Dual cycle is than the diesel cycle and than the otto cycle for the same compression ratio.

Ans: greater, less.

86. What are the factors influencing of the Dual cycle?

Ans: 1. Compression ratio 2.cut off ratio 3. pressure ratio and 4. heat supplied at constant

volume and constant pressure.

87. The Brayton cycle is mainly used in

Ans: Gas turbine power plant.

88. Give the expression for efficiency of the Brayton cycle.

Ans:

1

Efficiency n = 1 - ---------- where Rp – pressure ratio. (Rp)y-1

89. The two stroke cycle engine gives the number of power strokes as compared to the four stroke cycle engine, at the same engine speed.

Ans : double.

90. In petrol engine, the charge is ignited with the help of

Ans : Spark plug

91. The diesel engine draws the mixture of diesel and air during suction stroke

(True / False)

Ans : False.

92. What is the fuel injector?

Ans : Fuel injector is used in diesel engine to inject and atomize the diesel at the end of

the compression stroke.

93. What is meant by SI engine ? Why it is called so ?

Ans : SI engine means spark ignition engine. In SI engine air fuel mixture is ignited by

spark plug hence it is called spark ignition engine. It is also called as petrol engine.

94. Give four major difference between two stroke and four stroke IC engine.

No

Two stroke cycle engine

Four Stroke cycle engine

1

One cycle is completed in two

stroke of the piston or one revolution of the crank shaft.

One cycle is completed in four

stroke of the piston or two revolution of the crank shaft.

2

For the same speed, twice the

number of power strokes are produced than 4 stroke engine.

For the same speed, half of the

number of power strokes are produced than 2 stroke engine.

3

Turning moment is more uniform

and hence lighter flywheel is used.

Turning moment is not uniform and

hence bigger flywheel is used.

clip_image0024 It contains ports which is operated by the piston movement.

It contains valves which is operated by valve mechanism.

95. What is meant by CI Engine ? Why it is called so ?

Ans : CI engine means compression ignition engine. In CI engine the fuel is injected by a fuel injector in atomized form because of high compressed air it gets ignited automatically. Hence it is called as compression ignition engine.

96. What is a two stroke engine ?

Ans : A two stroke engine is an engine in which one cycle of operation is completed in two stroke of the piston or one revolution of the crank shaft.

97. What is a four stroke engine ?

Ans : A four stroke engine is an engine in which one cycle of operation is completed in four stroke of the piston or two revolution of the crank shaft.

98. Name the four strokes of an IC engine?

Ans : Suction, compression, power and exhaust stroke.

99. Differentiate petrol and Diesel engines.

Petrol or SI engines

Diesel or CI engine

1. Combustion of air fuel mixture takes

place by spark produced by sparkplug.

1. Combustion takes place by high

compressed air.

2. Carburetor is used to mix the air fuel

mixture.

2. Fuel injector is used to inject the fuel in

atomized form.

3. Compression ratio varies from 6 to 8.

3. Compression ratio varies from 12 to 18.

4.It works on Otto cycle.

4. It works on Diesel or Dual cycle.

100. What is a Gas turbine? How do you classify.

Ans: Gas turbine is an axial flow rotary turbine in which working medium is gas. Classification of gas turbine.

1. According to the cycle of operation

a) open cycle b) closed cycle and c) semi – closed cycle.

2. According to the process

a) constant volume and b) constant pressure process.

101. What is meant by closed cycle gas turbine?

Ans: In closed cycle gas turbine, the same working fluid is recirculated again and again.

102. What is meant by open cycle gas turbine?

Ans: In open cycle gas turbine, the exhaust gas form turbine is exhausted to the atmosphere and fresh air is taken in compressor for every cycle.

103. Gas turbine is working on ----cycle

Ans: Brayton or Jules cycle.

104. How can we increase the efficiency of the gas turbine?

Ans: By providing inter cooler, re-heater along with heat exchanges.

105. Differentiate open and closed cycle gas turbines.

Open cycle gas turbine

Closed cycle gas turbine

1. Working substance is exhausted to the

atmosphere after one cycle.

1. The same working substance is

recirculated again and again.

2. Pre-cooler is not required

2. Pre-cooler is required to cool the exhaust

gas to the original temperature.

3. High quality fuels are used

3. Low quality fuels are used

4. For the same power developed size and

weight of the plant is small

4. Size and weight are bigger.

106. What is the function of intercooler in gas turbines? Where it is placed?

Ans: The intercooler is placed between L.P. and H.P. compressors. It is used to cool the

gas coming form L.P. compressor to its original temperature.

107. Why re-heater is necessary in gas turbine? What are its effects?

Ans: The expansion process is very often performed in two sperate turbine stages. The

re-heater is placed between the H.P. and L.P. turbines to increase the enthalpy of the exhaust gas coming from H.P. turbine.

Effects:

1. Turbine output is increased for the same compression ratio

2. Thermal efficiency is less.

108. What is the function of regenerator in gas turbine?

Ans: The main function of heat regenerator is to exchange the heat from exhaust gas to

the compressed air for preheating before combustion chamber. It increases fuel economy and increase thermal efficiency.

109. What is meant by single acting compressor?

In single acting compressor, the suction, compression and delivery of air take place on

one side of the piston.

110. What is meant by double acting compressor?

In double acting reciprocating compressor, the suction compressin and delivery of air

take place on both side of the piston.

111. What is meant by single stage compressor?

In single stage compressor, the compression of air from the initial pressure to the final pressure is carried out in one cylinder only.

112. Define clearance ratio

Clearance ratio is defined as the ratio of clearance volume to swept volume (or) stroke

volume.

Vc Vc – clearance volume

C = -------- Vs – swept volume

Vs

113. What is compression ratio?

Compression ratio is defined as the ratio between total volume and clearance volume.

Total volume

Compression ratio = ------------------- Clearance Volume

114. What are the factors that effect the volumetric efficiency of a reciprocating compressor?

1) Clearance volume 2) Compression ratio.

115. Compressor Capacity is

a) Volume of air delivered

b) Volume of air sucked c) Both a and b

d) Nine of the above

Ans: (a)

116. Compressor capacity is highest, when the intake air temperature is

Ans: Lowest

117. Compressor capacity is expressed in

Ans: m3/min

clip_image003118. As the compression ratio increases, the volumetric efficiency of air compressor

Ans: Decreases.

119.A 50 m3/min compressor can

a) Compress 50m3/min of free air

b) Compress 50m3/min of standard air c) Deliver 50m3/min of standard air

d) Deliver 50m3/min of free air.

Ans: a)

120. For delivering large amount of air at low pressure

a) Rotary compressors are used

b) Reciprocating compressors are used c) All engines are used

d) All the above

Ans: (a)

121. In gas turbine, type of rotary compressor used is

Ans: Axial flow compressor.

122. In Aeroplane, type of rotary compressor used is

Ans: Axial flow compressor.

123. What is the difference between complete (or) perfect inter cooling and incomplelte (or) imperfect inter cooling.

Perfect Inter cooling

When the temperature of air leaving the intercooler (T3) is equal to the original atmospheric air temperature (T1), then the inter cooling is known as perfect inter cooling.

Imperfect Inter cooling

When the temperature of air leaving the inter cooler (T3) is more than original atmospheric air temperature (T1), then the inter cooling is known as Imperfect inter cooling.

clip_image004124. Power requirement of a refrigerator is

Ans: Inversely proportional to cop

125. In SI Units, one ton of refrigeration is equal to

Ans: 210KJ/min

126. The capacity of a domestic refrigerator is in the range of

Ans: 0.1 to 0.3 tonnes.

clip_image005127. COP of a refrigerator working on a reversed carnot code is

Ans: T2

-----------

T1 – T2

128. The vapour compression refrigerator employs the cycle

Ans: Reversed carnot

129. In vapour compression cycle the condition of refrigerant is dry saturated vapour

Ans: Before entering the compressor.

130. Give the 4 important parameters that are to be measured and controlled of an air conditioning system.

1. Temperature of air

2. Humidity of air

3. Purity of air

4. Motion of air

131. Name the cycles on which an Air refrigeration system works.

Ans: 1. Reversed carnot cycle 2. Bell – coleman cycle

132. Name four important properties of a good refrigerant

Ans: 1. Low boiling point

2. High critical temperature & pressure

3. Low sp.heat of liquid

4. Non – flammable and non explosive.

133. Name some of the equipments used in air conditioning system

Ans: 1. Filter

2. Cooling coil

3. Heating coil

4. Compressor

5. Condeser

6. Evaporator

134. Name any four commonly used refrigerants

Ans; 1. Ammonia (NH3)

2. Carbon di oxide (CO2)

3. Sulphur di oxide (SO2)

4. Freon – 12.

135. What are the factors to be considered in air conditioning a room?

Ans: 1. Temperature of air

2. Humidity of air

3. Purity of air

4. Motion of air.

136. The door of a running refrigerator inside a room was left open. What will happen?

Ans: The room will be gradually warmed up.

137. Fourier’s Law is based on assumption that

Ans: Heat transfer in steady state

138. A perfect black body is one which

Ans: Absorb heat radiation of all wave lengths falling on it.

139. The valve of the wave length for maximum emissive power is given by

Ans: Wein’s Law

140. Thermal diffusivity of a substance is given by

Ans: k

--------- pCp

141. The unit for Stefan – Boltzman constant is

Ans: Watt/m2/k4

142. Two plates spaced 150mm apart are maintained at 1000°C and 70°c. The heat transfer will take place mainly by

Ans: Radiation.

143. Heat conducted through unit area and unit thick face per unit time when temperature difference between opposite faces is unity is called Ans: Thermal conductivity

144. The amount of radiation mainly depends on

Ans: Nature of body, temperature of body and type of surface of body

145. What is meant by radiation shape factor?

The space factor is defined as the fraction of the radiative energy that is diffused from

one surface element and strikes the other surface directly with no intervening reflections. It is represented by Fiji. Other names for the radiation shape factor are view factor, angle factor, and configuration factor.

146. Give the 3 basic expressions governing the 3 modes of heat transfer.

1) Fourier Law of conduction

dT

Q = -KA ---------- dx

where A – Area in m2

dT

---- - Temperature gradient in K/m dx

K – Therma conductivity W/mK

2. Newton’s Law of cooling

Q = hA(Ts - T∞)

Where

H – heat transfer co – eff in W/m2K

A – Surface Area in m2

Ts – Surface Temperature in K T∞ - Fluid Temperature in K

3. Stefan – Boltzman Law

Eb = σ T4

Where

σ - Stefan Boltzman constant = 5.669 x 10-8 w/m2 k4

T – Temperature in K

147. Define a black body

Black body is on ideal surface having the following properties.

1) A black body absorbs all incident radiation regardless of wave length and direction.

2) For a prescribed temperature and wave length, no surface can emit more energy than black body.

148. Given two examples of heat transfer with internal heat generation.

1. Chemical Reaction

2. Nuclear Reaction

3. Combustion Reaction.

149. Name the law which governs convection heat transfer

Ans: Newton’s law of cooling

150. Write down the Stefan Boltzman law with its Unit

The total energy emitted by a black body at a particular temperature is given by

Eb = σ T4

Where σ – Stefan Boltzman constant – 5.669 x 10-8 w/m2k4

STRESS STRAIN AND DEFORMATION OF SOLIDS Two Marks Questions With Answers 2014

Anna University, Chennai

Anna_University,_Chennai_logo

DEPARTMENT OF MECHANICAL ENGINEERING

Sub. Code/Name: ME 2254 / Strength of Materials Year/Sem: II/III

2 Marks

UNIT – 1 STRESS STRAIN AND DEFORMATION OF SOLIDS

1. Define stress

The force of resistance per unit area, offered by a body against deformation is

known as stress. Mathematically stress is written as,

clip_image001

Where σ = Stress

P= External force or load

A= Cross- Sectional area

2. Define strain

When a body is subjected to some external force, there is some change of

dimension of the body. The ratio of change dimension of the body to the original dimension is known as strain.

Strain may be:

1. Tensile strain 2. Compressive strain

3. Volumetric strain, and 4. Shear strain.

3. Define elastic limit

The limiting value of force up to and with in which, the deformation

completely disappears on the removal of the force. The value of stress corresponding to this limiting force is known as the elastic limit of the material

4. State Hokes law

Hokes’s Law states that when a material is loaded within elastic limit; the

stress is proportional to the strain produced by stress.

5. Define shear stress and shear strain

The stress induced in a body, when subjected to two equal and opposite forces which are acting tangentially across the resisting section, as a result of which the body tends to shear off across the section, is known as shear stress. The corresponding strain is known as shear strain. The shear stress acts tangential to the area. It is represented by Ï„.

6. Define poison’s ratio

The ratio of lateral strain to the longitudinal strain is constant for a given

material, when the material is stressed within the elastic limit. This ratio is

called Poisson’s Ratio and it is generally denoted by μ

clip_image002

7. Define Young’s modulus

The ratio of tensile stress or compressive stress to the corresponding strain is a

constant. This ratio is known as Young’s Modulus.

clip_image003

8. Define Modulus of Rigidity.

The ratio of the shear stress to the corresponding shear strain within elastic

limit is known as Modulus of Rigidity or Shear Modulus. This is denoted by C

or G or N.

clip_image004

9. Define Factor of Safety

It is defined as the ratio of ultimate tensile stress to the working stress.

Mathematically it is written as

clip_image005

10. Define Strain energy

Whenever a body is strained, energy is absorbed in the body. The energy,

which is absorbed in the body due to strained effect, is known as strain energy.

11. Define bulk modulus

When a body is subjected to the mutually perpendicular like and equal direct

stresses, the ratio of direct stress to the corresponding volumetric strain is found to be constant for a given material when the deformation is within a certain limit. This ratio is known as bulk modulus.

clip_image006

12. What is compound bar?

A bar, made up of two or more bars of equal lengths but of different materials

rigidly fixed with each other and behaving as one unit for extension or compression when subjected to axial tensile or compressive loads, is called a composite bar.

13. Define lateral strain

The strain at right angle to the direction of applied load is known as lateral

strain.

clip_image007

14. Define Thermal stresses.

The Stresses induced in a body due to change in temperature are known as thermal stresses.

15. Define thermal strain

If the ends of the body are fixed to rigid supports, so that its expansion is

prevented, then compressive stress and strain will be set up in the rod. This strain is known as thermal strain.

16. What is the relation between three modules?

E = 2C (1+µ )

E = 3K (1-2µ )

Where, E= Young’s Modulus

C = Modulus of Rigidity

K = Bulk Modulus

µ = Poisson’s Ratio

17. Define Resilience.

The Total strain energy stored in a body is commonly known as resilience.

Whenever the straining force is removed from the strained body, the body is capable of doing work. Hence the resilience is also defined as the capacity of strained body for doing work on removal of straining body.

18. Define Proof Resilience

The Maximum strain energy stored in a body is known as proof resilience. The

strain energy stored in the body will be the maximum when the body is stressed upto elastic limit. Hence the proof resilience is the quantity of strain energy stored in ablody when strained up to elastic limit.

19. Define Modulus of Resilience.

It is defined as the proof resilience of a material per unit volume.

Mathematically,

clip_image008

20. What is the difference between suddenly applied load and Impact load?

If the load is constant throughout the process of deformation of the body, such a type of loading is known as suddenly applied load.If the load is dropped from certain height, before the load commences to stretch the bar that type of loading is known as Impact load.


UNIT – II BEAMS-LOAD AND STRESSES

1. Define beam?

A beam is a structural member subjected to a system of external forces at right

angles to its axis.

2. What is mean by transverse loading on beam?

If the loads on the beam are perpendicular to the axis of the beam then it is

called transverse type of loading.

3. What is cantilever beam?

A beam which is fixed at one end and free at the other end is known as

cantilever beam.

4. What is simply supported beam?

A beam supported or resting freely on the supports at its both ends is

known as simply supported beam.

5. What meant by overhanging beam?

If the end portion of a beam is extended beyond the support, such beam is

known as overhanging beam.

6. What is mean by concentrated loads?

A concentrated load is one which is considered to act at a point, although in

practice it must really be distributed over a small area.

7. What is uniformly distributed load?

A uniformly distributed load is one which is spread over a beam in such a manner that rate of loading “w” uniform along the length. The rate of loading is expressed as w N/m run. Uniformly distributed load is, represented by U.D.L.

8. What are the different types of beams?

1. Cantilever beam 2. Simply supported beam 3. Over hanging beam

4. Fixed beam 5. Continuous beam.

9. Define point of contra flexure? In which beam it occurs?

At some point, the B.M. is zero after changing its sign from positive from

negative or vice-versa. That point is known as the point of contra flexure or point of inflexion

10. What is meant by positive or sagging BM?

The bending moment at a section is considered positive if the bending

movement at that section is such that it tends to bend the beam to a curvature having concavity at the top as often called sagging moment

11. What is meant by negative or hogging BM?

Similarly the bending movement(B.M.) at a section is considered negative if the bending movement at that section is such that it tends to bend the beam to a curvature having convexity at the . The positive B.M. is often called sagging moment and negative B.M. as hogging moment.

12. Define shear force and bending moment?

The algebraic sum of vertical forces at any section of a beam to the right or left of the section is known as shear force.

The algebraic sum of moments of all the forces to the right or left of the section is known as bending moment.

13. When will bending moment is maximum?

The bending moment will be maximum at a point where the shear force is minimum.

14. What is maximum bending moment in a simply supported beam of span

L’subjected to UDL of ‘w’ over entire span?

clip_image009

15. In a simply supported beam how will you locate point of maximum bending moment?

The maximum bending moment in a simply supported beam will be at the

point where the shear force line crosses the base line.

16. What is shear force and bending moment diagram?

The shear force diagram is one which shows the variation of the shear force

along the length of the beam.

The bending moment diagram is one which shows the variation of bending moment along the length of the beam.

17. What are the types of loads?

The different types of loads are

1. Concentrated load or point load

2. Uniformly Distributed load

3. Uniformly Varying load.

18. What is bending stress?

The stresses introduced by bending moment are known as bending stresses

19. Define pure bending.

If a length of beam is subjected to a constant bending moment and no shear

force(Zero shear force) then the stresses setup in that length of the beam due to bending moment only and that length of the beam is said to be in pure bending or simple bending.

20. Write the theory of simple bending equation?

clip_image010

21. State any three assumptions of Theory of simple bending.

1. The material of the beam is homogeneous and isotropic

2. The value of young’s modulus of elasticity is the same in tension and

Compression.

3. The transverse sections which were plane before bending remain plane after

Bending also.

22. What is neutral layer of a beam?

If a beam is subjected to simple bending the top layer of beam is subjected to

compression and the bottom layer is subjected to tension. At a level between top and bottom, there will be a layer which is neither shortened nor elongated. This layer is known as Neutral layer.

24. Define Moment of Resistance.

Due to pure bending, the layers above NA are subjected to compressive

stresses where as the layers below NA are subjected to tensile stresses. Due to these stresses, the forces will be acting on the layers. These forces will have moment about the NA. The total moment of these forces about the NA for a section is known as Moment of Resistance of that section.

25. Define Section Modulus.

Section modulus is defined as the ratio of moment of inertia of a section about

the NA to the distance of the outer most layers from the NA. It is denoted by the symbol Z. Mathematically,

clip_image011


UNIT – III TORSION

1. Define Torsion?

A shaft is said to be in torsion, when equal and opposite torques are applied at

the two ends of shaft. The shaft is subjected to a twisting moment. This causes the shear stresses and shear strains in the material of the shaft.

2. What are the assumptions made in torsion equation.

Torsion is based on the following assumptions:

§ The material of the shaft is uniform throughout.

§ The twist along the shaft is uniform.

§ The shaft is uniform circular section throughout.

§ Cross-sections of the shaft, which are plane before twist, remain plain after twist.

§ All radii which are straight before twist remain straight after twist.

§

3. Define polar modulus

Polar modulus is defined as the ratio of the polar moment of inertia to the

radius of the shaft.

4. Write down the expression for power transmitted by a shaft.

2Ï€NTmean

Power(Watts) = ----------------- Where,

60

N = Speed of the shaft, rpm

T = Mean Torque transmitted, Nm.

5. Write the polar modulus for solid shaft and hollow shaft. π D3

Zp = ----------- where D = Diameter of solid shaft

16

o

Ï€ [D 4

- Di4]

Zp = --------------------- where, Do = Outer Diameter of hollow shaft

16 Do Di = Inner diameter of Hollow shaft

6. Why hollow circular shafts are preferred when compared to solid circular

shafts?

For the same power transmission and Material, the weight of hollow shafts are less compared to solid shaft.

7 . Write torsional equation

T Ï„ GÓ¨

------ = ------ = ------ where,

J r l

T = Torque Transmitted, Nm

J = Polar Moment of Inertia, m4

r = Radius of shaft, m

G = Modulus of rigidity, N/m2

Ó¨ = Angle of Twist, Radians, l = Length of Shaft, m

8. Write down the expression for torque transmitted by hollow shaft.

Π Do4 – Di4

Torque transmitted by a hollow shaft – T = -------Ï„[-----------------]

16 Do

Where Do = Outer Diameter of hollow shaft

Di = Inner diameter of Hollow shaft

Τ = Shear stress induced in the outer surface of the shaft

9. Write down the equation for maximum shear stress of a solid circular section in diameter D when subjected to torque T in a solid shaft.

The maximum shear stress induced at the outer surface of the solid shaft.

clip_image012

10. Define torsional rigidity

Tensional rigidity or stiffness of the shaft is defined as the product of modulus

of rigidity (C) and polar moment of inertia of the shaft (J).

Tensional rigidity = C x J.

11. What is composite shaft?

A shaft made up of two or more different materials and behaving as a single shaft is known as composite shaft.

12. What is a spring? Name two important types of spring.

Springs are elastic bodies which absorb energy due to resilience. The absorbed energy may be released as and when required. The two important types of springs are

1. Laminated or leaf springs

2. Helical springs

13. State any two functions of springs.

1. It will absorb energy when it is loaded and releases the absorbed energy as and when required

2. It will act as cushion

14. Define helical springs specify the type of helical springs Helical springs are the thick spring wires coiled in to a helix The two types of helical springs are

(i) Close coiled helical springs

(ii) Open coiled helical springs.

15. What is solid length of a spring?

The solid length of spring means the distance between the coils when the coils are touching each other. There is no gap between the coils. The soilid length is given by

Solid length = Number of coils x Diameter of the wire = nX d

16. Define spring rate (stiffness).

The stiffness of the spring is defined as the load per unit deflection.

W

S = --------- δ

Where W = Load and δ = Deflection

17. Define pitch of the spring.

The distance between to consecutive coils is known as pitch of the spring.

18. What is spring index (C)?

The term Spring index in relation to springs it means the ratio of the mean diameter of the spring to the diameter of the wire. The preferred index range is 4 to 12.

19. What is free length of spring?

This is the length over all of the spring in the fully unloaded position (free position).

21. What are the differences between closed coil & open coil helical springs?

Closed coil

Open coil

The wire is coiled so close that the plane containing each turn is nearly at right angle to the axis of helix

The spring wire is coiled in such away that, there is a large gap between the two consecutive turns and takes compression load also.

The helix angle is less than 10o

The helix angle is greater than 10o

Due to loading, spring will elongate

Due to loading, spring will contract

22. What is the use of wahl’s factor?

(i) The whals factor is used to account the stress due to direct shear and curvature stress of spring.

(ii) It is used to calculate shear stress induced in a helical spring bt considering shear stress due to twisting.

23. What kind of stress is introduced when an axial load acts on a closed coil spring?

Shear stress is introduced when an axial load acts on a closed coil spring.In addition direct shear stress due to load is introduced. Stress due to curvature of the wire is also introduced.

24. What are the assumptions made ina closed coil helical spring subjected to axial load?

The assumptions are

1. An element of an axially loaded helical spring, behaves essentially as a straight bar in pure tension.

2. The planes perpendicular to the bar axis do not warp or distort during deformation.

25. List out the uses of helical springs.

Automobiles and railway carriages

Shock absorbers

Reciprocating mechanisms and clock springs.


UNIT – IV

1.What are the methods for finding out the slope and deflection at a section? (i) Double Integration Method

(ii) Moment Area method

(iii) Macaulay’s method

(iv) Conjucate beam method

2. State mohr’s theorems.

(i) The change of slope between any two points is equal to the net area of the

B.M Diagram between these points divided by EI

(ii)The total deflection between any two points is equal to the moment area of

B.M Diagram between the two points about the last point divided by EI.

3. What is the relation between slope and deflection?

If y= deflection

Slope = dy/dx

4. State the equation for bending moment and shear force.

BM = EI d2y/dx2

SF = EI d3y/dx3

5. Give expression for determining slope at the supports of a simply supported beam carrying a point load at the centre.

clip_image016clip_image019Ó¨a = Ó¨b =

6. Give expression for determining deflection of a simply supported beam carrying a point load at the centre.

clip_image023clip_image026yc= -

7. Give expression for determining slope and deflection of a simply supported beam carrying a UDL over the entire span.

clip_image029

clip_image031

Ó¨a = Ó¨b =

clip_image034

clip_image036

clip_image039

yc =

8. What are the steps to be followed in determining slopes and deflections at any point of a beam using Macaulay’s method?

(i) Brackets are to be integrated as a whole.

(ii) Constants of integrations are written after the first term

(iii) The section, for which B M equation is to be written, should be taken in the last part of the beam.

9. What is the condition for maximum deflection in a beam.?

For maximum deflection, the slope dy/dx must be equal to Zero.

10. State the expression for determining slope in area moment method.

Area of BMD Ó¨b = ------------------

EI

11. State the expression for determining deflection in area moment method.

AX

y = --------- EI

12. What is a column?

A vertical member of a structure, which is subjected to axial compressive load and is fixed at both of its ends is known as a column.

13. What is a strut?

Strut is a member of a structure which is not vertical or whose one or both of its ends are hinged or pin jointed.

14. Specify how the long and short column will fail?

All short columns fail due to crushing where as long column will fail due to buckling or crushing.

15. What is buckling load?

The load at which the column just buckles is known as buckling load or critical load or crippling load.

16. Give the expressions for a column by Euler’s formula for different end conditions.

clip_image046P = When both ends are hinged

clip_image050P = When one end is fixed and other end is free

clip_image053clip_image055P = When both ends are fixed

clip_image058P = When one end is fixed and other end is hinged.

17. What is effective length of a column?

The effective length of a given column with given end conditions is the length of an equivalent column of the same material and cross section with hinged ends, and having the value of crippling load equal to that of the given column.

18. What is slenderness ratio?

Slenderness ratio is the ratio of the effective length of the column to the least radius of gyration.

clip_image061

clip_image063

Mathematically, Slenderness ratio =

19. State the limitation of Euler’s formula.

If the slenderness ratio is small, the crippling stress will be high. But for the column material, the crippling stress cannot be greater than the crushing stress. Hence when the slenderness ratio is less than a certain limit, Euler’s formula gives a value of crippling stress greater than the crushing stress. In this limiting case, we can find the value of l/k for which crippling load equal to crushing stress.

20. Specify the expression for Rankine’s formula.

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clip_image068

clip_image071

clip_image072

clip_image075

clip_image076

= +

P = Crippling load by Rankine’s formula

Pc = Crushing load

PE = Crippling load by Euler’s formula


UNIT – V Analysis of Stresses in Two Dimensions

1. When will you call a cylinder as thin cylinder?

A cylinder is called as a thin cylinder when the ratio of wall thickness to the diameter of cylinder is less than 1/20

2. In a cylinder will the radial stress vary over thickness of wall?

No, in the cylinders radial stress developed in its wall is assumed to be constant since the wall thickness is very small as compared to the diameter of the cylinder.

3. What is the ratio of circumferential stress to longitudinal stress of a thin cylinder?

clip_image077

4. What is the maximum principal stress in a thin cylindrical?

The maximum principal stress in a thin cylinder is circumferential stress.

clip_image078

5. What is the maximum shear stress in a thin cylinder? Circumferential strains,

clip_image079

6. For a thin cylinder, write down the equation for strain along the circumferential direction.

clip_image080

7. For a thin cylinder, write down the equation for strain along the longitudinal direction

clip_image081

8. Write the expression for hoop stress in thin cylinder due to internal presser

P.

clip_image082

9. Write the expression for longitudinal stress in thin cylinder due to internal presser P.

clip_image083

10. For a thin cylinder, write down the expression for volumetric strain.

clip_image084

11. What is the circumferential stress in a thin spherical shell subjected to

internal presser ‘P’?

clip_image085

12. Write is the volumetric strain in a thin spherical shell subjected to internal

presser ‘P’

clip_image086

13. Write the circumferential strain in thin spherical shell.

clip_image087

14. In a thin cylindrical shell if hoop strain is 0.2×10-3 and longitudinal strain is 0.005×10-3, find out volumetric strain.

Volumetric strain, ev = 2ec ea

= 0.2 × 10-3 +0.005 × 10-3

ev = 0.25 × 10-3

15. Different between thin cylinder and thick cylinder.

Thin cylinder

Thick cylinder

1. Ratio of wall thickness to the

diameter of cylinder is less that

1/20.

2. Circumferential stress is assumed to be constant throughout the all thickness.

1. Ratio of wall thickness to the

dia., of cylinder is more than

1/20.

2. circumferential stress varies from inner to outer wall thickness

16. Distinguish between cylindrical shell and spherical shell.

cylindrical shell

spherical shell

1. Circumferential stress is

twice the longitudinal stress.

2. It withstands low pressure than spherical shell for the same diameter.

1. Only hoop stress presents.

2. It withstands more pressure than cylindrical shell for the same diameter.

17. Write the equation for the change in diameter and length of a thin cylinder shell, when subjected to an internal pressure.

clip_image09018. What is the effect of riveting a thin cylindrical shell?

Riveting reduces the area offering the resistance. Due to this, the circumferential and longitudinal stresses are more. It reduces the pressure carrying capacity of the shell.

19. What do you understand by term wire winding of thin cylinder?

In order to increase the tensile strength of a thin cylinder to withstand high internal pressure without excessive increase in wall thickness, they are some times pre-stressed by winding with a steel wire under tension.

20. Define principal stresses and principal plane.

Principal stress: The magnitudes of normal stress, acting on a principal plances are known as principal stresses.

Principal planes: The planes which have no shear stress are known as principal planes.

21. Give the expression for maximum shear stress in a two dimensional stress system.

clip_image091

22. What is the radius of Mohr’s circle?

Radius of Mohr’s circle is equal to the maximum shear stress.

23. A bar of cross sectional area 600mm2 is subjected to a tensile load of

50KN applied at each end. Determine the normal stress on a plane inclined at 30° to the direction of loading.

A = 600 mm2

Load, p = 50KN

θ = 30°

clip_image092

Normal stress, σn = p cos2θ = 83.33× cos2 30° = 62.5N/mm2

24. Give the expression for stresses on an inclined plane when it is subjected to a axial pull.

Normal stress, σn = p cos2θ

clip_image093

Shear stress, σt = p/2 sin2θ

25. What is the use of Mohr’s circle?

To find out the normal, tangential, resultant stresses and principal stress and their planes.

26. What are the planes along which the greatest shear stresses occur?

Greatest shear stress occurs at the planes which is inclined at 45° to its normal

27. Write the expression for a normal stress on an inclined plane in a block which is subjected to two mutually perpendicular normal stresses and shear stresses?

clip_image094

28. At a point in strained material is subjected to a compressive stress of

100N/m2 and shear stress of 60 N/mm2.determine graphically or otherwise the principal stresses.

σ = -100 N/mm2

clip_image095

q = 60 N/mm2

29. In case of equal like principal stresses, what is the diameter of the Mohr’s

circle?

Zero.

30. What is the value of maximum shear stress when the principal stresses are

clip_image096

σ1 compression and σ2 tension?