8. See the girl lifting weights? She raises them above her head, holds them there for 30 seconds,
and then lowers them slowly and sets them down on the floor. When is she doing work on the
weights?
a) From the time she starts lifting them until the time she sets them down,
because when they are on the floor they have the least G.P.E.
b) Only while she is lifting them up.
c) Only while she is holding them above her head.
d) The entire time she is moving them, but not when she is holding them
still.
- Work can be done in 2 ways: to change the speed of an object, and...