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Homework Help: Energy problem

  1. Dec 8, 2008 #1
    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. jcsd
  3. Dec 8, 2008 #2
    Your s=distance? also since when was work a vector quantity? and theta should be zero since the problem never mentions any angles.
     
  4. Dec 8, 2008 #3
    Yes. Sorry I didn't make that clear.
     
  5. Dec 8, 2008 #4
    check my edit
     
  6. Dec 8, 2008 #5
    I got it. Thanks for your help.
     
  7. Dec 8, 2008 #6
    No problem just curious is this high school physics?
     
  8. Dec 8, 2008 #7
    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.
     
  9. Dec 8, 2008 #8
    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).
     
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