Coetticient of Friction???

Sorry spelled tital wrong i ment Coefficient.

Im reviewing old stuff for my midterm and came across this, coefficient of friction i know its extremly easy but how???

Example question: You have a block of wood on a wooden board, you tilt the board up until the block slides (this happens at 30 degrees) what is the Coefficient of friction???

 

Coefficient of friction used in friction force which is f = uN. Where u is the coefficient and N is the normal force.

On the incline, you set the force of gravity and friction equal to find the coefficient.

 

I yes i spelled title wrong on purpose

So i guess what im having trouble with is finding Fn(normal force) on an angle.

not sure what you mean by setting the force of gravity and friction equal?

 

Ok so i looked over this again and this is what i found.

Fg = force of gravity

F down = Force down the ramp.

Fn = the normal force, or the force perpindicular to the ramp.

Also,

F down = Fg sin[theata], were theata is the angel of the ramp.

Fn = Fg cos[theata], were theata is the angel of the ramp.

This is found when the forces are put "tip to tail" they form a right triangle.

Correct me im wrong or If i misspelled theata or miss-spell ... lol <3

 

Its spelled theta.

When doing these problems on a ramp, if you draw the free body diagram on the box, theres 4 forces. Gravity, friction, normal, and the applied force.

What you have so far is right. Now you have to sum the "horizontal" forces which are the friction and component of gravity.