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September 1, 2014

September 1, 2014

Posted by **Bobby** on Sunday, November 10, 2013 at 10:53pm.

- Phyics -
**Damon**, Sunday, November 10, 2013 at 11:49pmA = angle of board up

force up = weight of board = w

friction force max = .7 w

equal and opposite horizontal force on wall = .7 w

length of board = L

weight of board down = w at L/2

moment of that weight about foot of board = w(L/2) cos A

moment of horizontal wall force about foot of board = .7 w (L/2) sin A

so

.7 sin A = cos A

sin A/cos A = 1/.7 = 1.43 = tan A

so A = 55 degrees

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