Question

Which of the following must occur in order for work to be done?

Answer 1

"Work is done on an object if two things happen: (1) the object moves as a force is applied and (2) the direction of the object's motion is the same as the direction of the force."

Answer 2

how ever no work is done if object moves perpendicular to direction of motion
since w=force *displacment*cos(angle)

Answer 3

Alternatively, we can say that work done is negative of change of the potential energy of the object upon which work is done