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Homework Help: How would I go about graphing a momentum experiment? (Design Lab)

  1. Feb 4, 2013 #1
    1. The problem statement, all variables and given/known data

    Alright, for my design lab I've gotten around and figured out how I'm going to record the data, but when I saw I needed a graph, I'm not sure what to do. I can prove my experiment to be true without using a graph.

    This is because I essentially have a weighted object with a certain momentum going to hit a trolley, that will go down a track and then hit a force sensor, this is to prove the conservation of momentum.

    But I can't really graph the results.

    I mean, what you really need to do is the find out if the calculated kinetic energy (from the mass hitting the trolley) is really reflected in the force sensor readings.

    I'm stumped...

    How do I use a graph for this...

    2. Relevant equations

    p = mv. (And knowing that the lowest point in a pendulum is where all the potential energy is turned into kinetic) (The mass hitting the trolley is swinging down from a pendulum)

    m1v1 = m2v2

    3. The attempt at a solution

    Not really one I can see
  2. jcsd
  3. Feb 4, 2013 #2


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    Staff: Mentor

    Momentum or energy?

    Do you know how force, time and momentum are related?
  4. Feb 4, 2013 #3
    Well, I'm supposed to be proving the conservation of momentum.

    So essentially, having the mass collide with the trolley will send a certain amount of energy into it, giving it a certain momentum, and that momentum should be reflected in the force meter's reading when it impacts it.

    momentum is Mass * Velocity.
    I can get the kinetic energy the trolley will recieve when impacted by the mass using MGH. (for potential) (As it will all be kinetic at the base of the pendulum)

    Then, since Ke = 1/2mv^2
    I can solve for v, getting the velocity.

    Then I can calculate momentum via p= MV.

    And then since Force = Mass * distance. (Or displacement?)

    Then MV = MS, and I have S(distance) and M would cancel.

    Then...well you got me. (lost now sorry, doing lots of work at the same time)

    EDIT: But force = ma, so I'm wrong..... GREAT.
    Last edited: Feb 4, 2013
  5. Feb 4, 2013 #4


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    You cannot prove momentum conservation. You can observe it, you can check it for your setup, and you can use it to predict things, but there is no way to prove a fundamental rule of physics.

    I agree


    To repeat my question: Do you know how force, time and momentum are related?
  6. Feb 4, 2013 #5
    I do not know, how force and momentum are related.
  7. Feb 4, 2013 #6


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    You can check the units (expressed in kg, m, s) to find some relation.
  8. Feb 6, 2013 #7
    Ah hA!

    Force * Time = Momentum.

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