CBSE Class 9 Answered

Potential energy is the capacity for doing work that a body possesses because of its position or condition

. For example, a stone resting on the edge of a cliff has potential energy due to its position in the earth's gravitational field.

If it falls, the force of gravity (which is equal to the stone's weight; see gravitation) will act on it until it strikes the ground; the stone's potential energy is equal to its weight times the distance it can fall.

Kinetic energy is energy a body possesses because it is in motion. The kinetic energy of a body with mass m moving at a velocity v is one half the product of the mass of the body and the square of its velocity, i.e., KE = 1/2mv². Even when a body appears to be at rest, its atoms and molecules are in constant motion and thus have kinetic energy.