Energy
Energy
“The capacity of a body to do work is called its energy”.
Types of energy:
There are two types of mechanical energy.
1) Kinetic energy
2) Potential energy
Kinetic energy:
“ The energy possessed by a body due to its motion is called kinetic energy”.
Mathematically:
K.E = ½ mv²
Where,
m = mass of the body and, v = velocity of the body
Kinetic energy is a scalar quantity.
Unit:
Unit of kinetic energy is joule.
Dimension:
[ ML²T²]
K. E is directly proportional to the mass of the object.
Potential energy:
“The energy possessed by a body due to its position in a force field. E.g , gravitional field or due to its constrained state is called potential energy”.
Gravitional Potential energy:
“ The potential energy due to gravitional field near the surface of the earth at a height ‘h’ is called the gravitional potential energy”.
Mathematically:
P.E. = mgh
Explanation:
The gravitional potential energy is always find out with reference to some point whose potential energy is taken as zero.
The two points taken as zero reference level of gracitional P.E. are.
1) The surface of earth
2) A point at infinity from the earth
Elastic potential energy:
“ The energy stored in a compressed spring due to its compressed or stretched state is called elastic potential energy”.
Mathematically:
P.E. = ½ K x²
Where
K = spring constant, and X = extension
Electric potential energy:
The energy acquired by a acharge as it passes through some potential difference is called electric potential energy.
Mathematically:
P.E.= Vq
Where
V = potential difference, and q = charge
Work Energy Principal:
Whenever work is done on a body, it increases its energy. For example a body of mass m is moving with velocity Vi, A force F acting through a distance d increases the velocity to Vf then from equation of motion
Multiplying eqs.
Absolute potential energy:
“ The work done by the gravitional force on a body in moving it from the surface of earth to infinity where the force of gravity becomes zero is called its gravitional potential energy”.
Mathematically:
U = - GMm / r
Escape Velocity:
“ The velocity with which the body goes out from the earth’s gravitional field is called escape velocity”. It is approximately 11km/s
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