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Homework Help: Collision with Angles

  1. Nov 2, 2008 #1

    uno

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    1. A skater with a mass of 81 kg is traveling east at 6.4 m/s when he collides with another skater of mass 45 kg heading 60° south of west at 13 m/s. If they stay tangled together, what is their final velocity, and direction in degrees (south of east)



    2. Vix = M1V1/M1+M2 and Viy = M2V2/M1+M2



    3. for Vix = 4.11 and Viy = 4.64. I'm not sure what the next step is. please help.
     
  2. jcsd
  3. Nov 2, 2008 #2

    uno

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    o.k. I figured out how to find the speed and the Vf = 4.38 m/s. Does anyone know how to figure out the final angle?

    Thanks
     
  4. Nov 2, 2008 #3

    uno

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    This is the reply I got from my professor:
    #15 is a two-dimensional collision that is totally inelastic since the objects stick together after the collision. Example 7.10 shows the solution for a similar problem, although it has one initial velocity of zero and #15 does not. Nevertheless, the example demonstrates that you set up a separate conservation of momentum equation for the x-components and a separate one for the y-components. I find it easiest to measure all angles from the positive x-axis; then the calculator automatically supplies all of the correct signs for the velocity components. For example, the velocity component in the x-direction for mass 1 before the collision is v[1,i,x] = v[1,i] cos (theta[1,i]). The velocity component in the x-direction for masss 2 after the collision is v[2,f,x] = v[2,f] cos (theta[2,f).

    But I don't think it helps with finding the final angle...does it?
     
  5. Nov 2, 2008 #4

    uno

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    I tried to take 4.64/4.11 = 1.13. I then to the cotan of that answer to get 48.47 degrees. Am I on the right track?

    Thanks
     
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