The coefficient of sliding friction from a static start.

[damianov]

Hello all - This is my first post, so please be gentle. I have a general question about the coefficient of sliding friction. An object, say a flat stone, is at rest on an incline at 30 degrees to the horizontal. Is it possible to calculate said coefficient without knowing the mass of an object?

 

[nasu]

Hello.
The mass does not matter.
Unfortunately you cannot calculate the coefficient unless you know that this 30 degrees is the maximum angle at which the stone is in equilibrium.
One simple lab experiment consist actually in increasing the angle of the plane (slowly) until the object starts to slide. Once you find this maximum angle (A_max) the coefficient of friction is tan(A_max).
If the angle is just an arbitrary angle (less than the maximum) then you cannot calculate the coef. of friction from the given data.

 

[damianov]

Thanks for that.