Answer
(a) (i) The work done by tension is zero.
(ii) The work done by gravity is zero.
(b) (i) The work done by tension is zero.
(ii) W = -25.1 J
Work Step by Step
(a) (i) The force of tension acts at a $90^{\circ}$ angle to the direction of motion. Therefore, the work done by tension is zero.
(ii) Since there is no net change in height, the work done by gravity is zero.
(b) (i) The force of tension acts at a $90^{\circ}$ angle to the direction of motion. Therefore, the work done by tension is zero.
(ii) The change in height is $2\times 1.60~m = 3.20~m$.
We can find the magnitude of work done by gravity.
$W = mgh$
$W = (0.800~kg)(9.80~m/s^2)(3.20~m)$
$W = 25.1~J$
Since the direction of gravity is opposite to the change in height, the work done by gravity is negative.
Therefore, $W = -25.1~J$
