WORK :
Work is said to be done, if force acting on a body is able to actually move it through some distance in the direction of the force. Its SI unit is a joule.
ENERGY :
1. Energy is a scalar quantity and its unit is Joule.2. The sum of all kinds of energies in an isolated system remains constant at all times. This is the law of conservation of energy.
POWER:
1. Its unit is watt.2. 1 watt hour = 3600 Joule
3. 1 kilowatt hour = 3.6 x 106 joule
4.1HP = 746 watt
GRAVITATION:
1.Everybody in the universe attracts other body by a force called force of gravitation.2. The gravitational force of the earth is called gravity.
3. The acceleration produced in a body due to force of gravity is called acceleration due to gravity (g) and its value is 9.8 m/s'
4. Acceleration due to gravity is independent of shape, size and mass of the body.
5.Escape velocity is the minimum velocity with, which an object just crosses the Earth's gravitational field and never returns. Escape velocity at the Earth's surface is 11.2 km/s.
6.Escape velocity at the Moon's surface is 2.4 km/s.Due to low escape velocity there is no atmosphere on the moon
7. Value of g decreases with height or depth from Earth surface.
8. g is maximum at poles.
9. g is minimum at equator.
10. g decreases due to rotation of Earth.
11. g decreases if angular speed of Earth increases and increases if angular speed of Earth decreases.
12. The acceleration due to gravity at the moon is one-sixth that of the Earth. So, the weight of a person on the surface of the moon will be 1/6 of his actual weight on the Earth.
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