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Inelastic Collision At An Angle

  1. Mar 25, 2013 #1
    Two objects of mass M (= 1 kg) each travel with identical speed (|v1| = |v2| = 3 m/s) making an angle of θ relative to the x-axis. After they collide with each other, they travel as one object of mass 2M and with a velocity v3 (|v3| = 2 m/s) in the horizontal direction.

    fig1.gif

    What is the value for angle θ in radians?

    I tried m1 * v1 * cos(θ) + m2 * v2 * cos(θ) = mf * vf, but that was just a blind attempt to try something.

    It's a practice exam question so I know the answer, but I want to know how to get there.
     
  2. jcsd
  3. Mar 25, 2013 #2

    SammyS

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    Hello Saendy. Welcome to PF !

    Use conservation of momentum.

    What's the momentum of the system (total momentum) before the collision?

    What's the momentum of the system after the collision?
     
    Last edited: Mar 25, 2013
  4. Mar 25, 2013 #3
    Hi Sammy, thanks for replying!

    The total momentum before should be:

    Pi = (m1 * v1) + (m2 * v2) = (3*1) + (3*1) = 6

    The total momentum after should be:

    Pf = (2m * vf) = (2*2) = 4
     
  5. Mar 25, 2013 #4

    SammyS

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    Don't forget v1 andv2 are vectors. Momentum is too.

     
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