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Old Oct 2nd 2014, 03:13 PM   #1
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Problem about Physics

I got this problem:
A wedge of mass m = 36.1 kg is held in place on a fixed plane that is inclined by an angle θ = 21.3 with respect to the horizontal. A force F = 302.3 N in the horizontal direction pushes on the wedge, as shown in Figure 4.25a. The coefficient of kinetic friction between the wedge and the plane is μk = 0.159. Assume that the coefficient of static friction is low enough that the net force will move the wedge.

http://semmedia.mhhe.com/physics/bau...dge/index.html
basically what's there except friction would be the other way around (since its accelerating up the slide.

I did a free body diagram and got:
Summation of forces in y:
Normal force = mg sin theta + Appliedforce sin theta

Then for the forces in x:
mgcos + friction - Aplliedforce sin = 36.1a

I did solve for everything but strangely the acceleration gives me acceleration = 3.2

Can any1 help me if im doing something wrong? Like getting cos and sin mixed?
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Old Oct 3rd 2014, 07:52 AM   #2
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In the y-direction (vertical direction, with positive up) the normal force is Ncos(theta), weight is -mg, the applied force is 0, and the friction force is umg sin(theta). In the x-direction with positive to the right the normal force is N sin(theta), weight is 0, applied force is -F, and friction is -umgcos(theta). Now try it again.
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