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Inelastic collision at an angle with two cars

  1. Oct 30, 2006 #1

    huh

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    almost there-inelastic collision at an angle

    Two cars, both of mass m, collide and stick together. Prior to the collision, one car had been traveling north at speed 2v, while the second was traveling at speed v at an angle phi south of east. After the collision, the two-car system travels at speed v(final) at an angle theta east of north.

    I want to find v(final) in terms of v and phi.

    Only momentum is conserved, so would I just use m1(2v1)+m2v2cos(phi)=(m1+v1)v(final)sin(theta)

    or could it be (m1+m2)2vcos(phi) divided by (m1+m2)

    I'm not sure how to set up the equation...I've been confusing myself...
     
    Last edited: Oct 30, 2006
  2. jcsd
  3. Oct 30, 2006 #2

    huh

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    Please help me understand.
     
  4. Oct 30, 2006 #3

    radou

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    You mixed the sines and cosines up - it should be: m(2v)+m(v)sin(phi) =(2m)v(final)cos(theta)
     
  5. Oct 30, 2006 #4

    huh

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    Thanks. okay, so...

    m2v+ mv sin(phi) divided by 2m cos(theta) is v(final)?

    how can I get v(final) with only v and Phi? I can't have m or theta in the equation.
     
  6. Oct 31, 2006 #5

    radou

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    Well, to get rid of m, you can obviously divide the whole equation by m. :smile:
     
  7. Oct 31, 2006 #6

    huh

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    Wouldn't there be an extra m on the bottom, and how could I get rid of theta and be left with phi, or does theta count for much (is it negligible)?
     
  8. Oct 31, 2006 #7

    radou

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    Since momentum is a vector quantity, you can write the equation of conservation of momentum for the other direction, too. (The x-direction.) That should allow you to elliminate the angle phi.
     
  9. Sep 27, 2008 #8
    what does v final look like?

    waht do u mean write the equation of momentum for the other direction?
     
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