Ahand lifts a block vertically upward at constant velocity. the work done by gravity on the block if the system consists of the block only. and why?
a) is zero,
b) is zero/is zero,
c) is negative/is zero,
d) is positive/is negative,
e) is negative/is positive,
f) is positive

Aclarinetist, setting out for a performance, grabs his 3.350 kg clarinet case (including the clarinet) from the top of the piano and carries it through the air with an upward force of 24.65 n. find the case's vertical acceleration. indicate an upward acceleration as positive and a downward one as negative.