- #1

KungFu

- 9

- 1

- Homework Statement
- A man with mass m_1 is in an elevator with mass 2m_1. The elevator accelerates vertically up at a rate a and at a certain time t has a speed V . The man climbs a vertical ladder within the elevator at a speed v relative to the elevator. What is the man's power output?

- Relevant Equations
- Newtons second law for finding the apparent weight F of the man

and then

finding the power output P = apparent weight times the speed

I have found the apparent weight of the man in the accelerating elevator

My question is about what speed I should use in the formula for the power output P = F ⋅ speed

My common sense tells me that the speed I should us is the speed v the man is climbing the ladder , because if the climbingspeed is zero then the man is standing still on the latter and is therefore not spending any energy.

However, the answer in the book is using the total speed, that is v + V , the sum of the climbingspeed and the elevator speed. Why ?

My question is about what speed I should use in the formula for the power output P = F ⋅ speed

My common sense tells me that the speed I should us is the speed v the man is climbing the ladder , because if the climbingspeed is zero then the man is standing still on the latter and is therefore not spending any energy.

However, the answer in the book is using the total speed, that is v + V , the sum of the climbingspeed and the elevator speed. Why ?