Question

Under what condition can work done by a force be negative?​

Answer 1

† Question:-

Under what condition can work done by a force be negative?

† Answer:-

The work done by a force can be negative only when the force acts in the opposite direction of the force applied or diaplacement.

• W = - F × s

Examples of negative work -

• The work done by the gravitational force, when we are lifting a bucket of water from the well.
• The work done by the buoyant force, when a stone is sinking.

Here, the force is opposite to the direction of motion.

Answer 2

Explanation:

(i) If the displacement of the body is in the direction of force. then work done is positive.

Hence, F×S

For example: A coolie does work on the load when he raises it up against the force of pavity. The force exerted by coolie (=mg) and displacement. both an in upward direction.

(ii) If the displacement of the body is in the direction opposite to the force. then work done is negative.

Hence, W=−F×S

For example: When a body moves on a surface. the force of friction between the body and the surface is in direction opposite to the motion of the body and so the work done by the force of friction is negative.