1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: 2D Momentum and Collisions Lab Help Grade 12

  1. Apr 12, 2012 #1
    1. The problem statement, all variables and given/known data

    For a lab, I have performed a completely inelastic collision using 2 masses. One mass is 0.583 kg, and the other is the unknown we have to find. Using an air table, I was given the dots to show the movements of the objects as they intersect and them move together. I have broken them into components and solved for the velocity and the momentum for each. Well, thats where the problem is:

    Momentum of the known mass:

    m1v1 = p1
    m1x(v1x) = p1x
    m1y(v1y) = p1y

    Same thing for the second mass, except it is m2, an unknown.

    When they move together, I know the mass will be the total (m1 + m2, which i state as m3) and the velocity will also be something else, v3.

    Now, the problem:

    I am trying to do m1v1 + m2v2 = m3v3 to find the unknown mass Question is, how would i rearrange the equation to find this m2.

    2. Relevant equations

    mv = p

    3. The attempt at a solution

    I am just trying with the 'x' component for the example:

    m1 = 0.583 kg
    v1x = 0.18 m/s [E]

    m2 = unknown
    v2x = 0.29 m/s [W]

    m3 = m1 + m2
    v3x = 0.05 m/s [W]

    m1v1 + m2v2 = m3v3

    How can i find this mass, it cancels out the moment I bring one of the m2's to the other side , I am I making some mistake here? I know it may not seem like I did any work, but I have pages of work getting to this part haha.
  2. jcsd
  3. Apr 12, 2012 #2
    what else could you call m3?
  4. Apr 12, 2012 #3
    m3 is (m1 + m2)
  5. Apr 12, 2012 #4
    i think you should show your work so far. there is no reason anything should cancel out.
  6. Apr 13, 2012 #5
    I got it, thanks.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook