Posted by Amy on Sunday, February 17, 2013 at 4:35pm.
A block of mass 3 kg is at rest on an incline. The coefficient of state friction between the block and incline is 0.34. What is the maximum angle of the incline such that the block will not slide down the plane?

Physics  Henry, Monday, February 18, 2013 at 5:17pm
Wb = m * g = 3kg * 9.8N/kg = 29.4 N. = Wt. of the block.
Fb = 29.4N. @ Ao. = Force of the block.
Fp = 29.4*sinA = Force parallel to the incline.
Fv = 29.4*cosA = Force perpendicular to the incline.
Fs = u*Fv = 0.34 * 29.4*cosA = 10*cosA.
FpFs = m*a.
29.4*sinA10*cosA = m*0 = 0
29.4*sinA = 10*cosA
Divide both sides by cosA:
29.4*(sinA/cosA) = 10
Replace sinA/cosA with tanA:
29.4*tanA = 10
tanA = 0.34
A = 18.8o