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Chapter 2

Forces And Motion

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Maximumdiplacement

Total energy= mgh

Simple Pendulum

Total energy = Kinectic energy +

Potential energy

Total energy

Energy

Displacement

KineticenergyGravitational

potential

energy

Solution

Question A ball is released from the top of a building, 20 m tall. What is the velocityof the ball when it reaches the surface of the Earth?

Gain in kinetic energy = Loss of gravitational potential energy

Velocity of object, v = 2gh = 2 10 20 = 20 m s1

mv2 = mgh12

Gravitational Potential Energy

Gravitational potential energy of an objectdue to its position

m: mass of objectg: acceleration due to gravityh: height of the object from

the earths surface

Kinetic Energy

Kinetic energy of an object due to its motion

m: mass of object v: velocity of the object

The Principle Of Conservation Of Energy

The total energy in a closed system is constant.

Ep = mgh

Ek= mv212

A ying bird has

kinetic energy

Finalposition

Initialpositionm

m

h

Surface ofthe Earth

Path 2

Work done= mgh

Path 1

Work done= mgh

Water falls due to

gravitational potential

energy