Question

Which of the following is an example of work?

		a weight lifer holding a heavy bar above his head
		a custodian pushing a broom across the gym
		a student thinking of the answer to a test
		your sibling pulling on a door that won't move because you locked it

Answer 1

When a force is apppied on an object and the object displaces, work is done by the force as long as there is some component of displacement of object in the direction of applied force. The magnitude of work done is given by product of applied force and displacement of object measured along the direction of force.

Therefore, in the given scenarios,

First scenario does not have anybwirk involved in holding the bar since there is no displacement involved.

Second scenario does have work done since there is applied force and displacement in direction of applied force

Third scemario of student thinking doesn not involve force and displacement and therefore no work done

Fourthly, there is no displacement since the door is locked. Therefore, no wrk in fourth option.

Only second option has work done.