# Homework Help: Find minimum work

1. Mar 2, 2010

### cmed07

I have been trying this problem multiple times but it still says i'm wrong:

What is the minimum work needed to push a 800 kg car 930 m up along a 9.0^\circ incline?

i'm using the formula:
W= Fdcos(theta)
F= mg

what am i doing wrong?

2. Mar 2, 2010

### tiny-tim

Welcome to PF!

Hi cmed07! Welcome to PF!

(have a theta: θ and a degree: º )

First, what is the minimum possible value of F?

3. Mar 2, 2010

### Andrew Mason

There are a couple of ways to approach this. One way is to calculate the component of force (gravity) along (ie. parallel to) the $$9.0^\circ$$ inclined surface and multiply that force by the distance (930 m). The simpler way would be to determine the height increase over that 930 m and the resulting change in gravitational potential energy of the car. The work is equal to the change in gravitational potential energy.

AM

4. Mar 2, 2010

### cmed07

Re: Welcome to PF!

That's all the information that was given to me... I know i'm supposed to find force by multiplying the mass and gravity...but i think the number i'm getting after i put it into the work formula is too big...

5. Mar 3, 2010

### tiny-tim

D'oh!

On the information that was given to you, what is the minimum possible value of F?