Answer
(a) $W = -5100~J$
(b) $W = 5100~J$
(c) $W = 0$
(d) $W_{total} = 0$
(e) Gravity is a conservative force.
Work Step by Step
(a) $W = -mgh = -(75~kg)(9.80~m/s^2)(7.0~m)$
$W = -5100~J$
(b) $W = mgh = (75~kg)(9.80~m/s^2)(7.0~m)$
$W = 5100~J$
(c) $W = mgh = (75~kg)(9.80~m/s^2)(0)$
$W = 0$
(d) $W_{total} = -5100~J + 5100~J + 0$
$W_{total} = 0$
(e) I would say that gravity is a conservative force. The starting point and ending point of the worker's journey are the same point and the total work done on the worker by gravity is zero. Therefore, gravity is a conservative force.
