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Homework Help: Frictionless blocks

  1. Jun 27, 2009 #1
    1. The problem statement, all variables and given/known data

    What is the magnitude of force F (which is pushing from the left on M) required to keep M1 and M2 relatively at rest to M?

    Ignore all friction.

    See attached diagram

    2. Relevant equations

    Newton's laws

    3. The attempt at a solution

    Well...If M is at rest, M1 and M2 will have an acceleration due to M2's weight.
    When force F appears though, M2 will be pushed horizontally by M since they are in contact.

    That's all I know atm.

    Attached Files:

    • M.png
      File size:
      4.8 KB
  2. jcsd
  3. Jun 27, 2009 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    The question asks about a force on M that allows "M1 and M2 to remain relatively at rest to M".

    So what is the condition between M1 and M, such that M1 stays at rest with respect to M? If M1 does not move with respect to M, the M2 doesn't fall.
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