Question

you are pushing a shopping cart. if you take items out of your cart but push at the same distance how does your work change?your work will?

a. increase because you have less to push
B. decrease because you have less to push
C. not change because distance does not change
D. can't be determined from the information given

Answer 1

(C)

Answer 2

That was wrong

Answer 3

Agreed. C is not the right answer. You can push with less force is mass is removed from the cart. If you assume the force applied is the same, you will reach a different conclusion than if the force applied is reduced. So the answer might depend on how you interpret the question and what assumptions are made. If you push the cart to maintain a constant speed, less work will be done, but if you push the cart to maintain a constant force, it will be the same. Most shoppers try to push the cart with a comfortable walking speed, so less force would be applied if mass were removed from the cart. The frictional force changes with the mass of the cart (and the normal force) so that complicates matters a bit.

Answer 4

Work = Force x Distance

Force = Mass x acceleration

Lowering the mass doesn't tell us anything about the acceleration of the cart. We could push the cart with a lower force, or a higher force, and thus the cart would accelerate less, or accelerate more, respectively.

Since we don't know anything about the acceleration of the cart between the two pushes, we can't really say whether or not the force increased, decreased, or stayed the same. Thus, we can't really say anything about the work done in this problem, at least not as it is stated.