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Tough Gun Recoil Question Literally!: Urgent Q

  1. Oct 9, 2006 #1
    The lead female character in the movie Diamonds Are Forever (lol so random) is standing at the edge of an offshore oil rig. As she fires a gun, she is driven back over the edge and into the sea. Suppose the mass of a bullet is 0.010 kg and its velocity is +720 m/s. Her mass (including the gun) is 51 kg. (a) What recoil velocity does she acquire in the response to a single shot from a stationary position, assuming that no external force keeeps her in place? (b) Under the same assumption, what would be her recoil velocity if, instead, she shoots a blank cartridge that ejects mass of 5.0 x 10^-4 kg at a velocity of +720 m/s?

    My Conflict- Well, I'm stuck on finding the Force and the wording on which mass to use is confusing (for parts A and B)...The equation I am using is
    Force x Time = Change Velocity x Mass -- This problem has something to do with Conservation of Linear Momentum. If you're trying to work this problem out, then the answer you should get for Part B is .0071 m/s. Anyways, PLEASE HELP...I need help ASAP! :confused: :confused:
  2. jcsd
  3. Oct 9, 2006 #2


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    You don't need the force. All you need is conservation of momentum. Before the bullet is fired, there is zero momentum. After it is fired the total momentum of the bullet plus the girl must still be zero.
  4. Oct 9, 2006 #3
    ok i will try it out and let you know in a bit! thanks buddy :smile:
    Last edited: Oct 9, 2006
  5. Oct 10, 2006 #4
    ^^^Hey, I got the answer right after the server crashed lol thanks!
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