- #1

deblimp

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## Homework Statement

A helicopter, starting from rest, accelerates straight up from the roof of a hospital. The lifting force does work in raising the helicopter. An 720-kg helicopter rises from rest to a speed of 7.5 m/s in a time of 5.0 s. During this time it climbs to a height of 7.9 m. What is the average power generated by the lifting force?

## Homework Equations

Gpe=mgh KE=1/2MV^2

## The Attempt at a Solution

Ok so we had a test today and afterwards we were discussing how to do one of the problems. Me and a classmate had two different ways to do this problem. He determined the net force acting on the helicopter by calculating the average acceleration and from there using the equation W=Fcos*X. I used conservation of energy to determine that the total energy in the problem using Gpe=mgh KE=1/2MV^2. From there we both divided by time to get teh power, not the work. Using these two methods does end up with two relatively different answers, so I was wondering which is the right method to use?