1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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: Sliding down a sliding plane

  1. Dec 5, 2009 #1
    1. The problem statement, all variables and given/known data

    A point particle of mass m is sliding down a wedge inclined at an angle of [tex]\alpha[/tex] to the horizontal. The wedge has a mass m and is free to slide on a smooth horizontal surface. When the mass has fallen a height h, what will be the speed of the wedge?

    2. Relevant equations

    3. The attempt at a solution

    I tried a kinematics approach with a lot of angle-bashing and eventually came up with:

    [tex]v = \frac{h}{g^2} \cot \alpha[/tex]

    But this is wrong, and I have a feeling this is too complex for kinematics

    I've thought about a conservation of energy approach with

    [tex]mgh = \frac{1}{2}mu^2+\frac{1}{2}mv^2[/tex]

    where 'u' is the speed of the particle and 'v' is the speed of the block, but I don't know how to divde up the speeds!

  2. jcsd
  3. Dec 5, 2009 #2


    User Avatar
    Homework Helper

    Have you tried the conservation of momentum? There's no external forces in the x direction, so horizontal momentum must be conserved.
  4. Dec 5, 2009 #3
    Thanks, I hadn't considered conservation of momentum, I think i've got it now
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook