Question

Consider the equation for “work done by a constant force”. Come up with and clearly describe a specific example where you might be applying a force on an object but no “work” is being done. Then come up with an example where we see a force doing positive work, clearly describe the situation. Which of the pair would you rather spend your time doing? Explain why.

Answer 1

Work done is given by:

W = F d cos(theta)

where, F is the force ; d is the distance moved ; theta is the angle between F and d

Suppose we are applying the force on an object and it did not move/displace then no work will be done. Example pushing a heavy box and it did not move.

W = F x 0 = 0 J

Also when a work being done on the object with force perpendicular to the direction of motion, in that case also no work will be done.

since theta = 90 deg and W = F d cos90 = 0 J

When you try to move a box, with force, F = 50N , in horizontal direction ; and it displaces in +X with d = 10 m

W = F d cos(theta) = 50 x 10 x cos0 = 500 J.

Second one as the work done is resutling into something which is required to be done.