# Energy problem

1. Dec 8, 2008

### ChairmanMao

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

The asteroid has a mass of 4.10 x 10^4 kg, and the force causes its speed to change from 7100 m/s to 5700 m/s.

If the asteroid slows down over a distance of 1.50 x 10^6 m, determine the magnitude F of the force.

2. Relevant equations

w = -3.6736e11 J (I figured this out from a question before it that I didn't post)
F = W/(s(cos(theta)))

3. The attempt at a solution

F = (-3.6736e11) / ((1.50 x 10^6)(cos(theta)))

I was just wondering how you would find theta for this problem.

2. Dec 8, 2008

Your s=distance? also since when was work a vector quantity? and theta should be zero since the problem never mentions any angles.

3. Dec 8, 2008

### ChairmanMao

Yes. Sorry I didn't make that clear.

4. Dec 8, 2008

check my edit

5. Dec 8, 2008

### ChairmanMao

I got it. Thanks for your help.

6. Dec 8, 2008

No problem just curious is this high school physics?

7. Dec 8, 2008

### enricfemi

it seems that you have the right formulas. maybe you just complicated the question in high school.it wants us to find out the force in a giving distance, assuming that the force must be a constant of vector in the same direction of movement.

but for physics, i quite agree with you. we cant figure it out without theta.
conclusion is that:don't take too much time for the question in the books.

8. Dec 8, 2008

### ChairmanMao

Actually, yes. It was a webassign problem and the only one I had left so I was pretty anxious to get it done before it was time for me to submit it (hence why I ended up here after a few seconds on google lol).