Question

A hand 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

Answer 1

Answer:(e)

Explanation:

If block is raised vertically upward then work done by force F to height h is given by

$W_F=F\cdot .h$

$W_F=Fh$

Work done by gravity will be equal and opposite to the work done by force F as object is moving with constant velocity i.e. net force on object is zero.