Exercise-11.3 Page: 152

1. What is the kinetic energy of an object?

Solution:

The energy possessed by a body by the virtue of its motion is termed mechanical energy or kinetic energy. Every moving object possesses mechanical energy. A body uses mechanical energy to try to work. Kinetic energy of the hammer is employed in driving a nail into a log of wood, mechanical energy of air is employed to run wind mills, etc.

3. Write an expression for the kinetic energy of an object.

Solution:

If a body of mass m is moving with a speed v, then its K.E. E k is given by the expression,

Ek = 1/2 m v2

Its SI unit is Joule (J).

4. The kinetic energy of an object of mass, m moving with a velocity of 5 ms-1 is 25 J. What will be its kinetic energy when its velocity is doubled? What will be its kinetic energy when its velocity is increased three times?

Solution:

class ninth work and energy

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