An elevator held by a single cable is ascending but slowing down. Is the work done by tension positive, negative, or zero? What about the work done by gravity? Explain

Explanation:

1.) Work = Force*Distance

2.) The direction of motion lies in the same direction as the tension in the cable. So the work done by tension would be positive.

3.) The direction of the weight (due to gravity) would act opposite to the direction of motion of the elevator, so work done by gravity becomes negative.

b.a device that inputs heat into a cool object

t = 1/400 h   ⇔ 0.0025 h ⇔ 9s ⇔ 0.15 m

any of the answers are correct.