Please help a momentum problem?

Cart 1 has mass 737 g and cart 2 has mass 867 g. Assume the track is frictionless, and the initial speed of cart 1 is 6.26 m/s and cart 2 is at rest. Find: v1 and v2 after the collision.

Thank you for your help.

Comments

  • Here's the link for conservation of momentum.

    http://en.wikipedia.org/wiki/Momentum

    m1*u1 + m2*u2 = m1*V1 + m2*V2

    Where,

    m1 = mass of cart 1 = 737 g = 0.737 Kg

    m2 = mass of cart 2 = 867 g = 0.867 Kg

    u1 = velocity of cart 1 before collision = 6.26 m/s

    u2 = velocity of cart 2 before collision = 0 m/s

    V1 = velocity of cart 1 after collision

    V2 = velocity of cart 2 after collision

    After the collision cart 1 will move at a V1 from the following equation:

    V1 = [ (m1-m2) / (m1+ m2) ]*u1 + [ (2*m2) / (m1+m2) ]*u2

    and cart 2 will move at a V2 from the following equation:

    V2 = [ (m2-m1) / (m1+ m2) ]*u2 + [ (2*m1) / (m1+m2) ]*u1

    We then have:

    V1 = [(737-867)/(737+867)] * 6.26 m/s + 0 = - 0.51 m/s

    Notice: negative sign on V1 means that cart 1 move backward after the collision.

    V2 = 0 + [2(737) / (737+867)] * 6.26 m/s = 5.75 m/s

    Notice: you can solve this problem using mass unit in either g or Kg and still get the same answers.

  • center of mass velocity = {(737*6.26)/(737+867)} = 2.88 m/s

    Before collision-

    In center of mass frame: u1 = 6.26 - 2.88 = 3.38 m/s; and u2 = 0-2.88 = -2.88 m/s

    After collision-

    In center of mass frame: v1 = -3.38 m/s; and v2 = -(-2.88) = 2.88 m/s

    After collision-

    In laboratory frame: V1 = -3.38+2.88 = -0.50 m/s; and V2 = 2.88 +2.88 = 5.76 m/s

    So cart1 will recoil with 0.50 m/s and cart2 will move forward with 5.76 m/s

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