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Homework Help: A mass and a frictionless ramp

  1. Nov 8, 2007 #1
    1. The problem statement, all variables and given/known data
    Well i have a tiny question here

    a 2 kg mass starts at rest and slides down a 10 m high, 15 m long frictionless ramp. At the bottom of the ramp it reaches a flat surface where it hits and sticks to a stationary 3 kg mass . Find the final speed of the masses after collision.

    2. Relevant equations
    mgh = .5mv^2

    3. The attempt at a solution

    i was just wondering does the 15 m really matter, where do i use it. I understand the second momentum part of the question but i dont understand what i am supposed to do with the 15 m. All i did was mgh = .5mv^2 and substituted height and mass to get velocity. Please Help.
  2. jcsd
  3. Nov 8, 2007 #2


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    Homework Helper

    Maybe it is not a head on collision in which case the angle is required?
  4. Nov 8, 2007 #3


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    When the mass slides down the frictionless ramp, its accelarion is not g but g*sin(theta) where theta is the angle of the ramp to the horizontal. And you can find sin(theta) by using length and height of the ramp.
  5. Nov 8, 2007 #4

    thanks for the help, actually i just omitted the length and used energy equations, and i got the right answer...go figure..
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