1. A pendulum has 15-J of potential energy at the top of its swing. What is its kinetic energy at the bottom of its swing?

a) At another time the pendulum has 8-J of potential energy. What is its kinetic energy?
b) For the pendulum in “a”, what will its kinetic energy be if it loses 2-J to heat?

What are you trying to ask?

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