i want to check my answer?

Question

A man lifts a 5 kg crate from the floor to a shelf (9 m high) at constant speed*.
(*Neglect the very start and very end of the lift, where the crate would of course need to be accelerated from/to rest.)

a.) What is the work done by the man on the crate? J
b.) What is the work done by gravity on the crate? J
c.) What is the net work done on the crate? J
d.) Since the crate is lifted at constant speed, what should the change in its KE be? Is this confirmed by part c?
441 J

Answer 1

b. mgh 5*9.8*9
a. 0
c.same as b
d. ke =.5 *5*vsquare

Answer 2

The man is lifting the crate; therefore, increasing its gravitational potential energy.

a. Work = m*g*h = 5kg*9.8m/s^2*9m = 441 J

b. Gravity is not doing any work on the crate. Work = 0 J

c. Net work = total change in energy constant speed implies that kinetic energy is unchanged, potential energy increases by 441 J, Net work then is 441 J

d. I answered this in part c. Constant velocity means no change in kinetic energy.

I agree with your result.