# Homework Help: Need help with a Work and Energy problem

1. Dec 13, 2011

### suzukits

1. The problem statement, all variables and given/known data
A car of weight 7000N travels at a steady speed of 8m/s up a steady incline at 15degrees above the horizontal. The car's motion is opposed by a constant frictional force of 500N.

2. Relevant equations
Calculate:
a) the gain in p.e per second
b) the work done per second against friction
c) the car's engine power.

3. The attempt at a solution
I keep getting the wrong answer. It would be easier if I knew the distance traveled by the car but I don't know any suitable formula.

Help is appreciated!

2. Dec 13, 2011

### PhanthomJay

Welcome to these forums!

The car travels 8 m along the incline every second (given).

3. Dec 13, 2011

### technician

In a way you do know the distance because the question is asking for the gain in PE per second and you know how far the car travels in 1 second (8m/s)
Hope this gets you into the question

4. Dec 13, 2011

### suzukits

Does that mean that the answer should be in Watts? Since its J/s?

5. Dec 13, 2011

### technician

Yes.... all the answers will be joules per second....ie watts

6. Dec 13, 2011

### suzukits

but what exactly does "gain in potential energy per second" mean?
is it just 8? since that's the velocity

7. Dec 13, 2011

### technician

PE is due to change in VERTICAL height .....mgh......?
The 8m/s is along the slope.....not vertical