- #1

theloathedone

- 18

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## Homework Statement

A man of weight W is in an elevator. The elevator accelerates vertically up at a rate a and at a certain instant has a speed V. The man then climbs a vertical ladder within the elevator at a speed v relative to the elevator. What is the man's rate of expenditure of energy?

## Homework Equations

P = Fv

## The Attempt at a Solution

So first, I found the apparent weight of the man as

[itex] w=W(1+\frac{a}{g}) [/itex]

which would be the force that he needs to exert in order to continue climbing.

I thought that the power required is just w*v (small v, the speed at which he is climbing in the elevator). But the answer states that it's w*(V+v), the total speed.

I was thinking that the power output should be the same whether the elevator just started to move and when it has already been accelerating for a certain time. So I'm not sure if the answer is wrong, or I've made a conceptual mistake.

Thanks in advance for the help!