Question

Block A is pressed against the wall by Force F, F=60 N, find friction force between block & wall. (${\mu }_s=0.8,{\mu }_k=0.7$)

• A. 48 N
• B. 42 N
• C. 40 N
• D. 36 N

Answer 1

The correct option is C 40 N


For equilibrium along direction $\perp$ to wall

F=N

N=60

$f_{max}={\mu }_{s}N=0.8\times 60=48$

Force || to surface $\Rightarrow mg=40$ N which is less than limiting friction. Hence,

f=40 N