Scalar and Vectors - Explanation

The motion of objects can be described by words. Even a person without a background in physics has a collection of words that can be used to describe moving objects. Words and phrases such as going fast, stopped, slowing down,speeding up, and turning provide a sufficient vocabulary for describing the motion of objects.

In physics, we use these words and many more. We will be expanding upon this vocabulary list with words such as distance, displacement,speed, velocity, and acceleration. As we will soon see, these words are associated with mathematical quantities that have strict definitions. The mathematical quantities that are used to describe the motion of objects can be divided into two categories.
The quantity is either a vector or a scalar. These two categories can be distinguished from one another by their distinct definitions:

• Scalars are quantities that are fully described by a magnitude (or numerical value) alone.
• Vectors are quantities that are fully described by both a magnitude and a direction.

Examples:

Scalar Quantity : Mass,Time,Temperature and Electric Potential.

Mass is a Scalar Quantity Because it is Fully Described by Size.

Ex:

5 m - Scalar Quantity

20 degrees Celsius - Scalar Quantity


Vector Quantity : Weight,Force,Velocity,Electric Field intensity and Electric Flux.


A Vector can be represented geometrically by an arrow. 

Weight is a vector quantity because it has direction ( the weight of an object pushes down due to gravity)

Ex: 

30 m/sec, East - Vector Quantity.

Thanks to:

Source: http://www.nasa.gov/ 

Source: http://www.physicsclassroom.com

Mass–Energy Equivalence

In 1905, Albert Einstein showed that, as a consequence of his special theory of relativity, mass can be considered to be another form of energy. Thus the law of conservation of energy is really the law of conservation of mass-energy.

In normal everyday interactions, the amount of mass that is transferred into other forms of energy (or vice versa) is such a tiny fraction of the total mass that it is beyond our sensory perceptions and measurement techniques. Thus, in a chemical reaction, for example, mass and energy truly seem to be separately conserved. In a nuclear reaction, however, the energy released is often about a million times greater than in a chemical reaction, and the change in mass can easily be measured.

Mass-energy equivalence entails that the total mass of a system may change, although the total energy and momentum remain constant; for example, the collision of an electron and a proton annihilates the mass of both particles, but creates energy in the form of photons. 

In physics, mass-energy equivalence is the concept that all mass has an energy equivalence, and all energy has a mass equivalence. Special relativity expresses this relationship using the mass-energy equivalence formula

E = mc²
where

E = the energy equivalent to the mass (in joules),
m = mass (in kilograms), and
c = the speed of light in a vacuum (celeritas) (in meters per second).

Origination of the formula is popularly attributed to Albert Einstein.

In the formula, c² is the conversion factor required to convert from units of mass to units of energy, i.e., the energy density. In unit-specific terms, E (joules or kg·m²/s²) = m (kilograms) multiplied by (299,792,458 m/s)2.

The discovery of mass-energy equivalence was essential to the development of theories of atomic fission and fusion reactions.

Some Images of Mass–Energy Equivalence :

4-meter-tall sculpture of Einstein's 1905 E = mc2 formula at the 2006 Walk of Ideas, Berlin, Germany

Funny : (E=mc2)

Source:

en.wikipedia.org/wiki/Mass–energy_equivalence

www.thefreedictionary.com/mass-energy+equivalence

Lorentz force - Explanation with Jumping Wires

The flow of an electric current down a conducting wire is ultimately due to the motion of electrically charged particles (in most cases, electrons) through the conducting medium. It seems reasonable, therefore, that the force exerted on the wire when it is placed in a magnetic field is really the resultant of the forces exerted on these moving charges.

The Lorentz force is the force on a point charge due to electromagnetic fields. It is given by the following equation in terms of the electric and magnetic fields:

where F is the force (in newtons)
E is the electric field (in volts per metre)
B is the magnetic field (in teslas)
q is the electric charge of the particle (in coulombs)
 v is the instantaneous velocity of the particle (in metres per second)
× is the vector cross product.

The implications of this expression include:

 1. The force is perpendicular to both the velocity v of the charge q and the magnetic field B.

2. The magnitude of the force is F = qvB sinθ where θ is the angle < 180 degrees between the velocity and the magnetic field. This implies that the magnetic force on a stationary charge or a charge moving parallel to the magnetic field is zero.

 3. The direction of the force is given by the right hand rule. The force relationship above is in the form of a vector product.

 Example :


A long length of wire is suspended horizontally between the poles of a magnetron magnet. When a large current from a 12V storage battery is passed through the wire, the wire jumps out of the magnetic field. When the direction of the current is switched, the wire jumps the opposite direction.

The magnetron magnet in this demonstration was originally used in MIT's groundbreaking research developing radar during and after World War II. Microwave emitting cavity magnetrons need strong magnetic fields, which were often created by powerful permanent magnets like the one used in this demo.