Question

State and explain work energy principle. Mention any three examples for it.

Answer 1

The work-energy principle states that an increase in the kinetic energy of a rigid body is caused by an equal amount of positive work done on the body by the resultant force acting on that body. Conversely, a decrease in kinetic energy is caused by an equal amount of negative work done by the resultant force.

Examples,

(1) A car is accelerating constantly. Here velocity is increasing. As a result of, kinetic energy is also increasing. So positive work is done.

(2) A ball is dropped from a certain height. Here velocity of the ball is increasing gradually due to gravitational acceleration. As a result of which kinetic energy increases and positive work is done.

(3) A motor bike applies break and comes into rest after few second. Here work done by the break is negative. Because speed decreases, for which K.E also decreases.