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Solving for distance with frictionless inclined plane

  1. May 23, 2013 #1
    A physics student shoves a 0.5 kg block from the bottom of a frictionless 30 degree plane. The student performs 4 joules of work and the block slides a distance "s" along the inclined pane before it stops. Find the value of s



    W = (F * Cosθ) * D



    I plugged in 4 joules for work, multiplied .5 kg by gravity(9.8) to get the force of the object which is 4.9N

    Equation I got for solving for D is:

    Not sure if algebra is correct

    d = work / F * Cosθ

    d = 4 / 4.9 * cos30

    d = .94 meters (rounded)

    Did I setup the equation correctly for D correctly and then solve properly?



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



    2. Relevant equations



    3. The attempt at a solution
     
    Last edited: May 23, 2013
  2. jcsd
  3. May 23, 2013 #2
    There are two ways you can approach this problem.
    1. Figure out the force required to push the mass up the ramp that is parallel to the surface of the ramp. Then use W = F X D to find D

    2. Since there is no friction, the work will be the change in potential energy of the mass. How high will the mass have to be raised to do 4 J of work. Then figure out how far to slide the mass to raise it this ammount.
     
  4. May 23, 2013 #3
    ya no clue what that means but thank you for trying
     
  5. May 23, 2013 #4
    Approach 1. Draw a diagram with the mass on the inclined ramp. What is the component of the weight (mg) that acts down the ramp? This is the force you have to overcome.

    Approach 2. The work done is equal to the change in potential energy of the mass. As you push it up the ramp, the height increases and so does the potential energy. If you know the increase in height, you can easily find how far you have to push the mass up the ramp to achieve this height.
     
  6. May 24, 2013 #5

    haruspex

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    To use a formula successfully, you need to know what the terms in represent. What do you think theta represents in the above equation? Which angle is that in this problem?
     
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