Help with Urgent Physics Incline Problem

AI Thread Summary
The discussion focuses on solving a physics problem involving a block on an inclined ramp with static friction and a wall. The first part requires finding the angle θ at which static friction can hold the block in place. For angles greater than θ, the wall assists in holding the block, necessitating a free-body diagram and equations to describe the forces acting on the block. The derived equation for the force from the wall, Fwall, is analyzed to determine the fraction of the block's weight supported by the wall as a function of the angle θ. The calculations and reasoning presented are aimed at confirming the validity of the results.
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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

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.
 
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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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