Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: 2D Motion of Sphere - Inclined Plane

  1. Feb 3, 2010 #1
    1. The problem statement, all variables and given/known data

    A small sphere is dropped from rest at a height 'h' above a plane inclined at an angle θ to the horizontal ( < 90degrees ). Given that the sphere loses no energy on impact, show that the distance down the plane between this impact and the next is 8hSinθ.

    2. Relevant equations

    3. The attempt at a solution

    Presumably, we need to consider a rotated reference frame oriented to apply to the given inclined plane. The component along the plane will have a Sinθ component, but I can't really put my finger on how to solve this.
  2. jcsd
  3. Feb 4, 2010 #2


    User Avatar
    Homework Helper

    After the first impact, the ball will recoil with velocity v making an angle θ with the perpendicular to the inclined plane.
    If A is the first point of impact and P is the next point of impact, then distplacement along inclined plane is
    AP = vsinθ*t + 1/2*gsinθ*t^2..........(1)
    Along the vertical direction to the inclined plane, the displacement is zero. So
    0 = vcosθ*t - 1/2*gcosθ*t^2 ...........(2)
    Find the value of t from the second equation and substitute in eq(1) to find AP.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook