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Homework Help: Friction with moving block question

  1. Oct 4, 2009 #1
    The drawing shows a large cube (mass = 49 kg) being accelerated across a horizontal frictionless surface by a horizontal force P. A small cube (mass = 4.6 kg) is in contact with the front surface of the large cube and will slide downward unless P is sufficiently large. The coefficient of static friction between the cubes is 0.71. What is the smallest magnitude that P can have in order to keep the small cube from sliding downward?


    Anyone have any idea?

    I tried both normal forces multiplied by the static friction coefficient.
  2. jcsd
  3. Oct 5, 2009 #2


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    Welcome to PF!

    Hi ethrust2! Welcome to PF! :wink:

    Hint: for a particular P, what is the acceleration of the small block?

    and so what is the reaction force on the small block? :smile:
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