How can I find the coefficient of friction for an object on an inclined plane?

[Jandaberg123]

Homework Statement

So I have and inclined plane at 1 degrees, and on top of it, there is an object 361grams. I gradually increase the angle of the inclined plane, and just at 20 degrees, the object starts to slide down. How do I find out the coefficient of friction?



Any help would be appreciated.

Thanks

Homework Equations

The Attempt at a Solution

I only know that just before it is about to slide down, mgsin20-Ffmax=0
so do i use 19.99999 degrees to solve this equation? So i used mgsin19.999=Usmgcos19.9999

and got 1.299999N but I think its wrong.

 

[tonit]

Not necessarily when resultant force is 0, the object does not move.

For example, take the case when you are pushing an object with a force $F$, and there is a friction $f$ equal to the force you are applying, the object moves with constant speed $v$, but there is no acceleration. $a = 0$.

$F$_resultant$= m*a$, so when $F$_resultant$= 0$ then you don't have acceleration.

So basically, you don't have to make it 19.9999999, it is 20 degrees.

I have attached a jpeg with the sketched problem. Have a look at it. Good luck