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Simple problem

  1. May 15, 2004 #1
    I'm doing some problems from an old text that seems to be plagued with errors in the answer key. I think my method is correct, but if someone could confirm my answers to this problem, I'd very much appreciative.

    Two girls sit on opposite ends of a sled 6.0 m long initially at rest on frictionless ice. Each girl has a mass of 50 k; the sled's mass is 30 kg. The girl at one end throws a 4.0 kg object to the other girl so that the obect travels horizontally at 5.0 m/s relative to the ice. What is the sled's speed (a) before the second girl catches the object? (b) After she catches the object? (c) Over what distance does the sled move while the object is in flight?

    My answers (a) 0.15 m/s (b) 0 m/s (c) 0.18 m

    The books answers (a) 1/6 m/s (b) 0 (c) 6/31m
  2. jcsd
  3. May 15, 2004 #2


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    How did you arrive at your answers?
    Last edited: May 15, 2004
  4. May 16, 2004 #3

    Doc Al

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    Staff: Mentor

    We obviously can't comment on your method, since you didn't share it. In the future, even when you just need an answer confirmation, please show us how you did the problem. After all, you took the trouble to type in the problems...a couple more lines won't kill you. :smile: (No need for all the gory details necessarily; just an indication of the principles you applied is often enough.)

    And, yes, your answers look good to me.
  5. May 19, 2004 #4
    Thanks guys. Sorry about not posting my method. I'll give more complete posts in the future and try to learn to LATEX. Well for the problem I assumed an isolated system and used the fact that the total momentum of an isolated system is constant. In this case [tex]p_{1}[/tex] + [tex]p_{2}[/tex]=0
    Thanks again
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