CBSE Class 9 Answered

Hi Aniket,

Kinetic energy:

The energy possessed by an object on account of its motion is known as kinetic energy.

Consider an object of mass m, moving with initial velocity u. Let it be displaced through a distance s when a constant force F acts on it in the direction of its displacement. The work done is

The work done on the object will cause a change in its velocity. Let its velocity change from u to v. Leta be the acceleration produced.

Thus, the kinetic energy of a body is

1. Directly proportional to the mass of the body

2. Directly proportional to the square of the velocity of the body

Potential energy:

The energy possessed by an object on account of its position or configuration is known as potential energy.

 The gravitational potential energy of an object at a point above the ground is defined as the work done in raising it from the ground to that point against gravity.

The force required to raise the object is equal to the weight F = mg of the object. If it is raised to a height h, then the work done is

W=mg x h

• This work is stored in the body as potential energy.

Work done by gravity depends on the initial and final positions and not on the path taken to raise it to the specified height.