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Homework Help: Momentum - two car system

  1. May 9, 2010 #1
    1. The problem statement, all variables and given/known data

    Two identical cars (m = 1350 kg) are traveling at the same speed (25 m/s). Car A is going 30 degrees East of North and car B is going 60 degrees West of North. What is the magnitude of the total momentum of the two-car system.

    2. Relevant equations

    p = mv

    3. The attempt at a solution

    I found the x and y components of the momentum of each car. Then i added the similar components together. So then to find the momentum of the system i took the sqrt of the x and y components squared and added together.

    x component car A
    1350kg(25m/s)(cos60) = 16875

    x component of car B
    1350kg(25m/s)(cos30) = 29228

    Total x component momentum = 46103

    y component of car A
    1350kg(25m/s)(sin60) = 29228

    y component of car B
    1350kg(25m/s)(sin30) = 16875

    Total y component momentum = 46103

    so the total momentum of the system is

    P_total = sqrt ((46103^2) + (46102^2))

    P_total = 65199 kgm/s

    This is wrong though.

    The correct answer is 47700 kgm/s

    Can anyone help me get the right answer.

    Thank you :)
  2. jcsd
  3. May 9, 2010 #2


    User Avatar
    Homework Helper

    x components of momentum are in the opposite direction.
    total x component momentum = ..........?
  4. May 9, 2010 #3
    x component of car B is actually

    -29228 so the total x component is -12353

    so the total momentum of the system is

    P_total = sqrt ((46103^2) + (-12353^2))

    P_total = 47730kgm/s


    Thank you
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