Juanita sticks a nail to the end of a bar magnet. She then sticks a second nail to the first, then another to that one, and so on. When she gets to the seventh nail, it falls off the sixth nail.
Which statement best describes the forces acting on the seventh nail?
The force of magnetism is equal to the force of gravity.
The force of gravity is stronger than the force of magnetism.
The force of magnetism is stronger than the force of gravity.

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

Iwould say earthquakes.