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Homework Help: Inclined plane and velocity

  1. Oct 24, 2004 #1
    Inclided plane


    I have a physics question.

    A block with mass m=14.7 kg slides down an inclined plane of slope angle 44.4* with a constant velocity. It is then projected up the same plane with an initial speed 2.55 m/s. How far up the incline will the block move before coming to rest?

    I know that Fnet in the x-direct (assuming x-axis is parallel to the inclined). is 0 since there is no acceleration, but constant V. Therefore Fparallel + -friction = 0. Uk = tan(44.4).

    On the way back up:
    Fnetx = ma
    Fapp + -f + -Fgx = ma
    This does not work out, as I get a to = 0.

    I need acceleration in order to find the distance travelled up the incline. Using
    Vf = Vi + 2ad

    If anyone could help me out it would be greatly appreciated.
  2. jcsd
  3. Oct 24, 2004 #2

    Doc Al

    User Avatar

    Staff: Mentor

    As you realize, on the way down the net force is zero. Use this fact to figure out the force of friction. Hint: On the way down, friction and gravity (the component parallel to the plane) act in opposite directions; on the way up, they act in the same direction. Use this fact to find the force and then the acceleration on the way up.

    Also: The kinematic equation you will need is [itex]v_f^2 = v_i^2 + 2ad[/itex].
    Last edited: Oct 24, 2004
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