1) A person with mass $m = 70kg$ takes an elevator from the ground floor to the
third floor at a height $h = 12m$. Assume the person doesn't move with respect to
the elevator and there is no air resistance. The elevator goes through the
following processes: accelerating from rest to moving at a speed $v = 1ms^{-1}$,
moving at constant speed $v$, decelerating to rest.
a) Draw the free-body diagram for the person in each of the three processes,
and mark in each case whether the normal force between the person and the
elevator is smaller than, equal to, or bigger than $mg$.
b) From the beginning to the end, what is the work done to the person by the
force of gravity?
c) When the elevator is at a height $h_1 = 6m$, the elevator is moving at the constant
speed $v$. What is the work done to the person by the normal force at that time?