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43
Unit 1.7: Energy, Work and Power
ENERGY
Energy is ability to do work
Its SI unit is “J” which stands for Joules
There are different forms of energy i.e
1)Kinetic energy:
Energy related with the motion of an object
Formula: ½(m)(v)^2 where “m” is mass of the object in Kilograms and “v” is
Velocity is m/s.
2)Gravitational potential energy:
Energy related with an object due to its position(height)
Formula: mgh where “m” is mass in Kilograms “g” is gravitational force
acting on the object (9.81N on Earth) and “h” is height of the object from
the surface in meters.
3)chemical energy:
Energy stored in humans, foods, batteries, and cells etc
4)elastic energy:
Energy stored in any stretched object
5)nuclear energy:
Energy given by nuclear power plant
6)electrostatic energy:
Energy stored in form of electricity
7)internal energy:
Energy related with molecules in any system
PRINCIPLE OF ENERGY: Energy cannot be created nor destroyed, it just
changes forms i.e energy is transferred during events and processes.
Example 1)
if an object is on a height of 10m and has mass 10kg then it has
gravitational potential energy of 981J and when it drops, energy is