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Need help

  1. Nov 5, 2007 #1
    1. The problem statement, all variables and given/known data

    A railroad car filled with sand is rolling with an initial speed of 20.0 m/s on straight, horizontal tracks. You can ignore frictional forces on the railroad car. The total mass of the car plus sand is 100,000kg. There is a hold on the floor of the car so sand leaks out the bottom. After 30 minutes, 15,000kg of sand has leaked out. Then what is the speed of the railroad car?

    2. Relevant equations


    3. The attempt at a solution

    Im not sure
  2. jcsd
  3. Nov 5, 2007 #2


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    Staff: Mentor

    Is the railroad car accelerating or decelerating?

    Certainly the car is getting lighter with the sand falling out, so it is loosing momentum and kinetic energy by virtue of loosing mass.
  4. Nov 5, 2007 #3
    The problem doesnt mention whether or not its accelerating. Thats the entire problem
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