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Homework Help: Incline/Pulley/Train combination problem (Dynamics)

  1. May 1, 2008 #1
    1. The problem statement, all variables and given/known data
    We have an assignment in physics class to design our own problem which must include these three concepts. I drew the FBD but when it comes to solving a combination problem like this I do not know where to start. Is this problem doable? Or do I have no idea how to make a problem =S. Basically I would like to know where to start solving the problem, and maybe some tip on improving it.

    1. The problem statement, all variables and given/known data
    The box of materials needed to complete the construction of the lighthouse weighs 4000 kg and is sitting at the bottom of the cliff. A pickup-truck that weighs 2500 kg, is connected to two carts consecutively, that weigh 500 kg, and 300 kg respectively. This system, which is on an incline, will pull the box of materials over the cliff with the help of a pulley. If the acceleration of the truck is 3m/s2 and the coefficient of friction between the truck and the surface is 0.05, calculate the amount of force needed to bring the box to the top of the cliff. The cliff is 30 degrees to the x-axis.

    M1 = 2500 kg
    M2 = 500 kg
    M3 = 300 kg
    M4 = 4000 kg
    a = 3m/s^2
    mu = 0.05
    Angle from x-axis to cliff – 30 degrees
    F = ?

    Hm. Guess I can't post images yet..
    The truck is going DOWN the incline, and the pulley is attached at the top, connecting M3 to M4(the materials).

    2. Relevant equations
    F=ma i guess..
    Last edited: May 1, 2008
  2. jcsd
  3. May 1, 2008 #2
    http://img151.imageshack.us/img151/4691/49736116bk9.jpg [Broken]

    for a rough drawing on the problem
    Last edited by a moderator: May 3, 2017
  4. May 4, 2008 #3


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    Homework Helper

    Hi arbitertrib,

    I don't understand which force you are asking for. The tension in the rope to pull up the object? The force of friction on the wheels of the truck to move it? Or something else? Since the truck is accelerating, no extra external force would be needed to lift the materials.

    Also, what is the coefficient of friction between the two carts already on the incline. Are they on wheels so that their coefficient is the same as the trucks?
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