Question

Mark weighs 375 N and is carrying a full-sized cello as he climbs the stairs to a height of 4 m. It takes him 3 seconds to do this.



How does the amount of work he does change if he were to climb the same flight of stairs again in the same amount of time, but this time without the cello?



A.
It increases.


B.
It remains the same.


C.
It decreases.


D.
It depends on the weight of the cello.

Answer 1

I'm going with C....

Answer 2

You are correct, but why?

Note that the time is not important when talking about work. Time only becomes important if you are given power, which has units of work per unit time, then you need to multiply power times time to get work. But that's not necessary here.

Here he does work, force times distance (his weight + weight of cello) * distance
Next he does work, force times distance (his weight alone ) * distance

Which is bigger?
(his weight + weight of cello) * distance

OR

(his weight alone ) * distance

That's what this question is asking.