Question

question #7
in which example would the amount of work done be equal to zero?
holding a picture in place on the wall.
pushing someone in a wagon.
picking up a puppy.
swinging a golf club.
question #8
work is equal to zero when
if the force and distance are not in the same direction or if the object does not move.
the force and distance are in the same directions.
the force and distance are equal in the same direction.

Explanation:

Work is defined as the product of force and displacement in the direction of the force ($W = Fd\cos\theta$, where $W$ is work, $F$ is force, $d$ is displacement and $\theta$ is the angle between force and displacement). When the object does not move ($d = 0$) or the force and displacement are perpendicular ($\cos\theta=0$), work is zero. In holding a picture in place on the wall, there is no displacement of the picture, so work done is zero. For question #8, work is zero when the force and distance are not in the same direction (specifically when perpendicular, $\cos\theta = 0$) or if the object does not move ($d = 0$).

Answer:

Question #7: Holding a picture in place on the wall.
Question #8: If the force and distance are not in the same direction or if the object does not move.