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Perfectly inelastic collision problem

  1. Nov 1, 2008 #1
    1. The problem statement, all variables and given/known data

    A 2000kg car moving east at 10 m/s collides with a 3000kg car moving north. They stick together and move as a unit after the collision, at an angle of 40 degrees north of east and at a speed of 5.22 m/s. Find the speed of the 3000kg car before the collision.

    2. Relevant equations
    mivi + mivi= mfvf + mfvf

    3. The attempt at a solution
    I tried plugging the numbers in the above equation but it did not work. The textbook gives the answer of 5.59 m/s and I cannot figure it out. Somebody give me some help please.
  2. jcsd
  3. Nov 1, 2008 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Since momentum is a vector you can break it into components. Write a separate conservation equation for east/west and north/south components. Once you have the components of the car's initial velocity, use them to find its speed.
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