# Question #7338e

Dec 25, 2016

#### Explanation:

Work is defined mathematically as

$W = F \Delta d \cos \theta$

The cosine term acts to project the force vector into the direction of the displacement.
For example, if $\Delta d$ lies in the $x$-direction, then only the component of F that lies in the $x$-direction contributes to the work done by the force.
In general, we consider only the component of F that acts in the direction of $\Delta d$ when evaluating the work done. (Of course, the magnitude of $\Delta d$ must not be zero.)

Choice 1 is too restricted and does not correctly allow for two-dimensional motion.
Choice 2 is completely wrong!
Choice 4 - what!?
Choice 5 - the object must move, or no work is done.
Choice 6 - Each force can do work on the object. The net force will determine the change in kinetic energy that results.