What is the speed of two railroad cars after they collide?

May 5th, 2009 | by Michael |
cars
finding.4ever asked:

Rail car dell'AMS m. is moving at speed? v when faced with a second railroad car of mas m. what? at rest. The two cars close together instantaneously and move along the track. What? speeed car immediately after the collision? How to get it?

JUNIOR

  1. 2 Responses to “What is the speed of two railroad cars after they collide?”

  2. By cathaychris on May 6, 2009 | Reply

    This problem involves momentum conservation.

    p = p’, which means the momentum before is equal to the momentum afterwards.

    To calculate the momentum of the system (which always includes both cars) before the collision, it is p= m * v + M * V (where v is the speed of the car in motion; V is the speed of the car at rest). Because V = 0, the momentum prior to the collision is simply m*v = mv.

    Afterwards, the mass of the system will be (m+M). To find the momentum, it’s (m+M)*v2 (which is just some velocity).

    Setting the two momentums equal,
    mv = (m+M)*v2
    Solving for v2,
    v2 = mv/(m+M)

  3. By Kevin on May 9, 2009 | Reply

    v1 - speed of car 1 before collision
    m = mass of car 1
    M = mass of car 2
    v2 = speed of car 2 = 0
    v3 = speed of both cars after collision

    mv1 +Mv2 = (m+M)v3

    v3 = m/(m+M)

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