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The acceleration of a ramp and mass

  1. Feb 4, 2015 #1
    [Mod note: Thread moved from New Member Introductions, so no template]

    I have a qns whereby a ramp of mass M rests on a frictionless floor and a mass m rests on the ramp, with no friction in between the mass and ramp. I need to find the acceleration of ramp M and mass m.
    I have the answers but I dont really understand them.
    aM= 2mgsinxcosx/M+m(sinx)^2 . I dont understand why is there a msin^2 term here
    am=[(M+m)gsinx]/M+(msinx)^2 . Again I dont understand why is there a msin^2 and how does M factor into the acceleration.
    Can someone pls teach mr how to get the ans?
     
    Last edited by a moderator: Feb 4, 2015
  2. jcsd
  3. Feb 4, 2015 #2

    Svein

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    Something is very wrong here.
    Dimensional analysis:
    • aM is force.
    • 2mgsinxcosx/M is acceleration.
    • m(sinx)^2 is mass.
    • am is force.
    • [(M+m)gsinx]/M is acceleration.
    • (msinx)^2 is mass.
     
  4. Feb 4, 2015 #3
    Oops Im sorry by aM I mean acceleration of M and by am I mean acceleration of m.
     
  5. Feb 4, 2015 #4

    Svein

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    You are still in trouble. According to your statement now:
    • aM is acceleration.
    • 2mgsinxcosx/M is acceleration.
    • m(sinx)^2 is mass.
    • am is acceleration.
    • [(M+m)gsinx]/M is acceleration.
    • (msinx)^2 is mass2.
     
  6. Feb 4, 2015 #5
    I am very sorry. I should have made this clearer.
    Acceleration of M=(mgsinxcosx)/[M+(msinx)^2]
    Acceleration of m=[(M+m)gsinx]/[M+(msinx)^2]
    It should be correct now
    I dont understand why is (msinx)^2 a mass component of the acceleration
     
  7. Feb 4, 2015 #6

    Svein

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    You are still wrong. If M and m are masses, (msinx)^2 is mass squared, and you cannot add mass and mass2 (whatever that might be).
     
  8. Feb 4, 2015 #7
    Exactly. That is what I dont understand about the ans. So is the ans given wrong?
     
  9. Feb 4, 2015 #8

    NascentOxygen

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    Staff: Mentor

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