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Homework Help: Need a setup for a fiction problem

  1. Oct 14, 2004 #1
    Need a setup for a friction problem

    I know the concept of this problem but i don't know how to set it up....

    'A large cube (mass= 25 kg) being accelerated across a horizontal frictionless surface by a horizontal force P. A small cube (mass= 4.0 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 0.17. What is the smallest magnitude that P can have in order to keep the small cube from sliding downward?'

    Thanks in advance
     
    Last edited: Oct 14, 2004
  2. jcsd
  3. Oct 14, 2004 #2
    anyone please help me
     
  4. Oct 14, 2004 #3
    P of the box needs to equal the normal force of the little box onto the big box. Draw two FBDs. On of a little box showing the effects of friction, a normal force and weight. Remember, the little box is in static equalibrium when referenced to the big box. The entire two box system may be accelerating due to force P but the comparison of the two boxs should help you figure this out.

    Draw a FBD of the big box as well. The N of the little box onto the big one equals the N of the big box onto the little BTW.

    Good luck.
     
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