Friction help. AP Physics C student

[bobAllan]

1. A 2.5 kg block is initially at rest on a horizontal surface. A horizontal force of magnitude F = 6.0 N and a vertical force of magnitude P are then applied to the block. The coefficients of friction for the block and surface are μ_s = 0.40 and μ_k = 0.25. Determine the magnitude of the frictional force acting on the block if ...
a) ...the magnitude of P is 8.0 N.

b) ...the magnitude of P is 10 N.

c) ...the magnitude of P is 12 N.


2

Fn=-mg
Ff=μFn



3.
honestly- not sure where to get started. i have the answers in the back of the book, but would really like to understand this and how to find hte solution

 

[PhanthomJay]

Please show some attempt at a solution for further assistance. You listed a couple of relevant equations, but neither is quite correct. Look at all forces in the y direction to calculate the normal force, and look up again the formula for friction.