Question

The angle between the resultant contact force and normal reaction force exerted by a body on the other when one is on the top

Answer 1

R be the frictional force'
R be the normal force
u= tan λ=F/R
When F =μR 
F is the limiting friction .
when applied force increases , force of friction increases upto limiting friction.
Before reaching limiting friction :
F <μR/F
tanλ=F/R < μR
tan λ≤ μ
λ≤ tan⁻¹μ

Answer 2

hey mate

here is ur answer.

i hope it helps you.