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Urgent help with physics incline problem

  1. Sep 27, 2009 #1
    Urgent help with physics incline problem!!!

    A block of mass m is on an inclined ramp. The coefficient of static friction between the block and the ramp is µs. There is also a wall on the ramp situated below the block (see diagram).

    http://img15.imageshack.us/img15/6056/image13pj.jpg [Broken]

    a) The angle of the ramp is increased. Up to a particular angle, θ, the force of static friction is able to hold the block in place. Find this angle.

    b) For angles greater than θc, the wall needs to assist static friction in holding the block in place. Draw a free-body diagram to show this, and write the equations describing the forces acting on the block. Call the force from the wall, Fwall.

    c) Solve the above equation for Fwall. Divide the equation you get for Fwall by the weight of the block to see what fraction of the weight is supported by the wall as a function of θ. Does your answer make sense? Explain why it does or does not.
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Sep 27, 2009 #2
    Re: Urgent help with physics incline problem!!!

    heres what i have

    b) Fnety= Fn-mg2cosθ
    m1a= mg1sinθ-Usm1gcosθ-Fwall
    m2a= mgsinθ-Usm2gcosθ

    c) Fwall= mgsinθ-Usm1gcosθ

    Fwall/m1g= (m1gsinθ-Usm1gcosθ)/m1g = Sinθ-Uscosθ

    look good?
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