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Homework Help: Distance traveled by a accelerating truck with steel load.

  1. Oct 14, 2007 #1
    Distance traveled by an accelerating truck with a steel load. With a twist!

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

    Consider a large truck carrying a heavy load such as steel beams. A significant hazard for the driver is that the load may slide forward crushing the cab, if the truck stops suddenly in an accident or even in braking. Assume, for example, that a 10,000kg load sits on the flat bed of a 20,000kg truck moving at 12.0m/s. Assume the load is not tied down to the truck and has a coefficient of static friction of 0.500 with the truck bed. Calculate the minimum stopping distance for which the load will not slide forward relative to the truck.

    2. Relevant equations

    Fsf is less then or equal to the coefficient of static friction * (mass * gravity)

    A= (velocity final - velocity initial) / (total time)

    change in x = original velocity in the x direction + acceleration in the x direction * time

    3. The attempt at a solution

    I know that both masses of the beams and truck are not relevant to the solution to the problem. However that's all I've been able to figure out. I think that if the truck is moving at 12m/s the bars must be resisting motion at 12m/s. Is this true? I wasn't sure which direction to go after determining that mass wasn't going to be any help. How could I use this to help solve the problem?

    The solution to the problem is 14.7m
    Last edited: Oct 14, 2007
  2. jcsd
  3. Oct 14, 2007 #2


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    Science Advisor
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    Gold Member

    The acceleration of the beam load must be the same as the truck's acceleration in order for the load not to slide with respect to the truck. You'll need to calculate that acceleration of the load using newton's 2nd law. The use your kinematic equations...you made in error in one of them for delta x.
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