# Power Problem

1. Oct 30, 2007

### dgoudie

[SOLVED] Power Problem

1. The problem statement, all variables and given/known data
A car (m = 760 kg accelerates uniformly from rest up an inclined road which rises uniformly, to a height, h = 45 m. Find the net power the engine must deliver to reach a speed of 25.1 m/s at the top of the hill in 20.7s (NEGLECT frictional losses: air and rolling, ...)

2. Relevant equations
P=W/T

3. The attempt at a solution

I tried to get through this but the computer said i had the wrong answer. Here's the hint it gave me:
Hint: Don't forget that the car has a non-zero speed at the top of the hill. Use conservation of energy, what is the total energy of the car at the top of the hill?

Most of this assignment has been on Work energy theorem. If anyone could give me a direction to go would be greatly appreciated

2. Oct 30, 2007

### Evalesco

Hi dgoudie,
Think of work as change in the net energy of the car. The net energy of the car at the top of the hill includes both its kinetic energy and grav potential energy.....

3. Oct 30, 2007

### dgoudie

So use$$\sum$$W = ef -ei?

Is the initial energy =0?

and Grav potential, is that mgh?

Alright nevermind i got it. thanks a lot!

Last edited: Oct 30, 2007