Question

Certain force acting on a 20 kg mass changes its velocity from 5 m s⁻¹ to 2 m s⁻¹. Calculate the work done by the force.

Answer 1

Kinetic energy is given by the expression,

Where,

= Kinetic energy of the object moving with a velocity, v

m= Mass of the object

(i) Kinetic energy when the object was moving with a velocity 5 m s⁻¹

2. Kinetic energy when the object was moving with a velocity 2 m s⁻¹

Work done by force is equal to the change in kinetic energy.

Therefore, work done by force =

= 40 − 250 = −210 J

The negative sign indicates that the force is acting in the direction opposite to the motion of the object.