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  • Feb 26, 2011, 09:48 PM
    western50
    momentum
    http://www.smartphysics.com/images/c...llisionnew.png

    A blue car with mass m@car = 444 kg is moving east with a speed of vc = 23 m/s and collides with a purple truck with mass m@truck = 1273 kg that is moving south with a speed of vt = 12 m/s . The two collide and lock together after the collision.

    What is the speed of the car-truck combination immediately after the collision? I think 10.702m/s

    Compare the initial and final kinetic energy of the total system before and after the collision: I think KEi > KEf




    http://www.smartphysics.com/images/c...twotrains2.png
    Now the same two cars are involved in a second collision. The first car is again moving to the right with a speed of v1 = 8.8 m/s and collides with the second train car that is now moving to the left with a velocity v2 = -6.2 m/s before the collision. The two cars latch together at impact. m1 = 679 kg, and m2=426.86kg

    What is the final velocity of the two-car system? (A positive velocity means the two train cars move to the right – a negative velocity means the two train cars move to the left.) I think 3.01m/s, right?

    Compare the magnitude of the momentum of train car 1 before and after the collision: I think it should be p1 initial > p1 final because of the change in velocity.
  • Feb 27, 2011, 05:28 AM
    Unknown008

    1. a. Right.
    b. You think? Either you do the calculation, or you use the fact that it's a completely inelastic collision and hence, energy is lost.

    2. a. Right.
    b. Right.

    You have to get more confident on your work. You do well, so... keep it up! :)

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