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This problem is driving me crazy

  1. Feb 25, 2007 #1
    This problem is driving me crazy!!!

    1. The problem statement, all variables and given/known data


    What is the magnitude of the force of the car on the truck, when the mass of the car is 1000 kg, when the mass of the truck is 2000 kg, when the driver steps on the accelerator, the wheels of the car push against the ground with a force of 4500 Newtons. What is the magnitude of the force of the car on the truck? The car is pushing the truck, just to clarify, not the other way around.

    The car is pushing the truck, there's no rope or chain or anything involved. It seems like theres some sort of information missing in this problem.

    2. Relevant equations

    F = m x a

    Force / Normal force = coefficient of friction

    3. The attempt at a solution

    I started off by assuming you could find the force by multplying the mass times the acceleration, because of the fact that the problem gives you so little information, but thats incorrect. (1000 x 9.807)

    I do know that all the forces given are in the y-direction, and theres no way to change that to x without finding the acceleration or the coeffecient of friction. I'm not quite sure if you can use the Newtons as the force to find a coefficient of friction, in which case I got 4500/9800, which is equal to .46 for the frictional coefficient, but I'm not sure if thats right or not.

    Someone please help!
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Feb 25, 2007 #2
    Have you considered using Newton's 3rd law for this problem? That is, try drawing a free body diagram, list all of the action/reaction pairs, and try to figure out what happens physically before you try applying mathematics.

    Also, I think you must be a little confused if you are using gravity as an acceleration because the car and truck will not be accelerating through the ground. In fact, Newton's third law would show that the weight of the cars on the earth is the same as the earth's push on the cars.

    *P.S. I think you are able to ignore friction in this case.
     
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