# Homework Help: How much energy is saved per airplane

1. Feb 17, 2008

### cstout

1. The problem statement, all variables and given/known data

An airline executive decides to economize by reducing the energy, and thus the amount of fuel, required for long distance flights. He orders the ground crew to remove the paint from the outer surface of each plane. The paint removed from a single plane has a mass of approximately 100 kg. (a) If the airplane cruises at an elevation of 26,000 m, how much energy is saved in not having to lift the paint to that altitude? (b) How much energy is saved per airplane by not having to move that amount of paint from rest to a cruising speed of 270 m/s?

2. Relevant equations

K=1/2mv2

W= Change in Kinetic Energy

3. The attempt at a solution
Part A - I don't know what to do

Part B.
K =(1/2)(100kg)(270)^2 ----but this is wrong

2. Feb 17, 2008

### PhanthomJay

I think in A they are asking for the savings in work done against gravity....that is, the savings in Potential Energy (PE). For B, I believe they are looking for the total energy savings with both PE and KE savings summed together.

3. Feb 17, 2008

### ||spoon||

in part a you must determine the amount of energy required to lift 100kg to an altitude of 26,000 m. Remember gravitational potential energy is given by Ug=mgh

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