Question

work and energy
under which condition is no work done?
a force pushes an object and slows it down.
a force pulls an object and speeds it up.
a force pulls down on an object that moves downward.
a force pushes up on an object that stays in place.

Explanation:

Work is done when a force causes an object to move in the direction of the force. When a force is applied to an object but the object does not move (stays in place), no work is done according to the physics - work formula $W = F\times d\times\cos\theta$ (where $W$ is work, $F$ is force, $d$ is displacement, and $\theta$ is the angle between the force and displacement vectors). In the case of an object staying in place, $d = 0$, so $W=0$.

Answer:

A force pushes up on an object that stays in place.