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Homework Help: Momentum Conservation, or not

  1. Jan 19, 2009 #1
    1. The problem statement, all variables and given/known data
    The problem I am having, is my physics teacher will not explain a solution that he is having us use for a lab, and so I dont know what values to use for the equation.

    The equation is to find the increase in momentum due to the work done by gravity. This is for a lab in which one metal ball berring is released from rest at a height 1.215 m above the ground. It swings downward on two strings, equal tension assumed, and strikes another ball at height .675 m above the ground, both ball are of equal mass. This ball then flies off the table and strikes the ground. The four reference frames are A: Both balls at rest, B: Ball on string was released and is about to hit the second ball at 3.255 m/s, C: second ball flies through the air and has an assumed air time of .371 sec., D: second ball is about to strike the ground. The problem is he wants us to use this equation, which I have no idea what to do with, and he won't tell us how to get these values.

    I am a high school senior in AP Mechanics, and this is only a small portion of the lab. I just need to know what I am supposed to use for these values.

    2. Relevant equations
    %(delta)P= [PDt-(impulse due to gravity)(from time A to B)(in the vertical direction) -(impulse due to gravity)(from time C to D)(in the vertical direction)]/[(impulse due to gravity)(from A to B)(total),{i think that is what the t means},+ (impulse due to gravity)(from Cto D)(total)]

    3. The attempt at a solution
    There is no real attempted solution on this, I just need to know what some of these values are supposed to be, because he writes one thing and says another over the phone, and has confused me to know end.
  2. jcsd
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