(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A 6.1-kg box is being lifted by means of a light rope that is threaded through a single, light, frictionless pulley that is attached to the ceiling.

(a) If the box is being lifted at a constant speed of 2.0 m/s, what is the power delivered by the person pulling on the rope?

(b) If the box is lifted, at constant acceleration, from rest on the floor to a height of 1.4 m above the floor in 0.42 s, what average power is delivered by the person pulling on the rope?

2. Relevant equations

P = F * v

KE = .5mv^2

W = F * distance

W = KE

3. The attempt at a solution

I've answered the first problem, getting .120 kW as an answer. But I'm having trouble with the (b), and maybe the concept of average power is throwing me off. I don't know what to do with the time given (0.42 s) and the height (1.4 m)...I know power is KE/T, but I don't know what the velocity is in KE since no acceleration was given. Thanks for your help! Much appreciated.

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# Relating Power to Work and KE

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