Mechanics Help (1 Viewer)

[kurenaishu07]

How do i prove this, also am i able to assume that coeff friction ≥0?

 

[liamkk112]

View attachment 43648
How do i prove this, also am i able to assume that coeff friction ≥0?

yes, if the coefficient of friction was negative then it wouldn’t be friction and it would be another force (because it wouldn’t be resisting your motion)

 

[wizzkids]

Yes, the coefficient of friction is always a positive number. The friction force always opposes the direction of incipient motion. If you are pushing the block up the ramp, the friction force acts down the ramp, and vice versa.
That's a strange way to describe the coefficient of friction, to say "When this occurs the friction force is F=μN".
That is always the case, not just in the limiting case of the angle of repose.
Anyway, on the way to deriving the final inequality, you should make use of this relation, that tan α = μ_s the static friction coefficient