physics question....?

Question

A block weighing 80 lbs is on a 32.2 degree inclined plane.
(a)
What is the force parallel to the plane?
(b)
What is the acceleration if there is no friction?
(c)
What is the coefficient of friction if the object is just at the point of sliding?
(d)
Find the acceleration of the block if the coefficient of sliding friction is 0.280.

Any help is greatly appreciated....

Answer 1

a) 80 lbs is a force. trig needed here to find how much of the 80 lbs is pointed downhill: sin(32.2)*80 lbs

b) convert the 80 lbs to mass. w = m*g. Then for acceleration, F = m*a.

c) The force of friction Ff equals answer a) because they just balance. Ff also equals mu*N where mu is the coefficient and N is a force normal to the slope: N = cos(32.2)*80 lbs.

d) Use the equation above, Ff = mu*N, to find the force of friction. If it's less than the answer to a), then there is some leftover force than will accelerate the block. Subtract and use the result in F = m*a.