A block of mass 4 kg is pulled by horizontal force $\mathrm{F}=12 \mathrm{~N}$. The block is still a

Question

A block of mass 4 kg is pulled by horizontal force $\mathrm{F}=12 \mathrm{~N}$. The block is still at rest. Coefficient of static friction between block and level surface is 0.4 . The frictional force developed in this case is

Professor PC Thomas Classes · Answer

Limiting friction $f_L = \mu_s N = 0.4 	imes (4 	imes 9.8) = 15.68 \mathrm{N}$. Applied force $F = 12 \mathrm{N}$ is less than $f_L$, so static friction adjusts itself to equal the applied force, which is $12 \mathrm{N}$.