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jwp0015

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**1. The homogeneous square body is positioned as shown. If the coefficient of static friction at B is 0.40, determine the critical value of the angle theta below which slipping will occur. Neglect friction at A.**

The image:

The image:

**2. N**

N

W=mg which is the weight in the negative y direction.

ƩF

ƩF

ƩM

_{A}is the Normal force at A, which is perpindicular to the 60° incline.N

_{B}is the Normal force at B, which is in the positive y direction.W=mg which is the weight in the negative y direction.

ƩF

_{x}=0ƩF

_{y}=0ƩM

_{B}=0 (the moment about B eliminates the unknowns N_{B}and F_{f}.**3. I have three pages of handwritten work. I started with the Moment about B, and took the moment arm from B to the center of mass (s/2)((sin∅-cos∅)i + (sin∅+cos∅)j. W is simply -Wj. I took the moment arm for the N**

I took the cross products and then summed the y forces and x forces. I have not been able to find equations to set equal to each other or substitue into each other to end up with an answer of (some tangent function of ∅) = (some number)

_{A}force to be s(-cos∅i + sin∅j). N_{A}=N_{A}(cos(30)i + sin(30)j). Putting all of those together into the ƩM_{B}= r1 x W + r2 x N_{A}= 0.I took the cross products and then summed the y forces and x forces. I have not been able to find equations to set equal to each other or substitue into each other to end up with an answer of (some tangent function of ∅) = (some number)

The answer to the problem is 20.7, but I have had no luck getting there. Thanks for the help ahead of time.