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Homework Help: Kinetic and Potential Energy on Ramps

  1. Dec 11, 2011 #1
    1. The problem statement, all variables and given/known data

    I don't want to tell the problem I just want to know how to solve it.
    There is a mass and a velocity and the ramp is inclined lets say 30 degrees.
    The object is going up the ramp with a force of friction opposing it. Find the distance the object travels before stopping.

    2. Relevant equations

    W = F (d)
    Eg = mgh
    Ek = 1/2(mv^2)

    3. The attempt at a solution
    let m = 5
    let v = 10

    Ek = 1/2(5(10^2))
    = 250 J

    W = 250 J
    250J = 4(d) ?
    62.5 = d ?

    Something wrong I am doing, all help is gratefully apppreciated.
  2. jcsd
  3. Dec 11, 2011 #2
    Part of the kinetic energy is lost due to friction, and part is converted to gravitational potential energy.
    Ef - Ei = -Fd = mgh - (1/2)mv^2
  4. Dec 11, 2011 #3
    Yes you did forget to subtract the frictional work from the original kinetic energy but once you find the vertical height the object rises you have to use the given angle to find how far up the ramp it will go.
  5. Dec 11, 2011 #4
    Yes you do subtract and then set the answer equal to mgh, the potential energy and then solve for the vertical height. But this isn't the answer to the question. The object moves up a ramp, not straight up so you have to draw the triangle showing the vertical height which you now know, the angle the ramp makes with the horizontal, which you given and then use the appropriate trig function to solve for the ramp which is the hypotenuse of the triangle.
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