A block of wood is sitting on an inclined plane. One end of the plane is rised until the wood block slides down. The wood block slides down when the plane has an angle of 30 degrees to the horizontal. What is the coefficient of friction?
Fnet = Fd + Ff
In this case, Fnet =0 because the wood block wasnt moving until 30 degrees.
The Attempt at a Solution
What I tried was drawing the free body diagram.
letting m=m, i get (Fd/sin30)=(Fn/cos30)
Substitute 0-Ff for Fd, and Ff/u for Fn.
this simplifies to -ucos30=sin30, giving u= -.577 or .577
Does this seem correct? I dont know what the right answer is but its odd that I got a negative answer and would love some confirmation that this is indeed correct .... or wrong :P