Coefficient of Friction when applied force is not horizontal to surface?

1. The problem statement, all variables and given/known data

What would happen to the coefficient of friction if the applied force was not horizontal to the surface?

2. Relevant equations
Ff=$$_{\mu}$$Fn

3. The attempt at a solution

I am unsure of how to proceed with this question, but I am thinking that you can't have friction against a vertical surface.
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 Quote by CharmedForever I am unsure of how to proceed with this question, but I am thinking that you can't have friction against a vertical surface.
Frictional force may certainly exist on a vertical surface.

 Quote by CharmedForever What would happen to the coefficient of friction if the applied force was not horizontal to the surface?
If by horizontal you mean normal to the surface then...

Ff = mu*Fn

Does Ff remain constant? No...it varies with mu and Fn. So what is mu dependant on? The two surfaces in contact! As the normal force changes, only the resultant frictional force varies, the coefficient of friction is constant between two surfaces and depends on the materials properties.

Coefficient of Friction when applied force is not horizontal to surface?

Well if u r nt apllying force in the horizontal direction u cn apply it in vertical direction bt if u aplly it perpendicular no friction takes place !! bt if u apply it with an angle u need to resolve vectors od cosθ and sinθ and hence find ur ans