Three forces act on an object, as indicated in the drawing. Force
has a magnitude of 21.0 newtons
(21.0 N) and is directed 30.0 to the
left of the "y axis. Force has a
magnitude of 15.0 N and points along
the axis. What must be the magnitude and direction (specified by the
angle # in the drawing) of the third
force such that the vector sum of the
three forces is 0 N?

What is the things about?

W= fd
where f is an applied force and d is the distance over which it is applied. when a parachuting skydiver is at constant velocity, he is experiencing "terminal velocity", the point at which his acceleration down is canceled out by air resistance. that means that the resisting force of the air is equal to his weight, but in the opposite direction. with this, we can solve for the work done by the force.
w = fd
w = (92.0)(9.81 m/s^2) (325)
w= 2.93 x 10^5 j
the value for work in this case is positive because it is pushing up on the skydiver, who has a downward force of gravity.
therefore the answer is 2.93 x 10^5 j

Because they're in different places for this the temperature varies.