Question

A block of mass $M$ is sliding down on a inclined plane. The co-efficient of static and kinetic friction between the block and the inclined plane is ${\mu }_s$ and ${\mu }_k$ respectively. Then friction force acting on the block is

• A. ${\mu }_k(F+Mg)\sin \theta$
• B. ${\mu }_k(F+Mg)\cos \theta$
• C. ${\mu }_{s}Mg\cos \theta$
• D. $(Mg+F)\tan \theta$

Answer 1

The correct option is B ${\mu }_k(F+Mg)\cos \theta$

As block is sliding, friction force will be kinetic in nature.


From FBD,

$N=(F+Mg)\cos \theta$

Since, block is sliding

$\therefore f={\mu }_{k}N$

$\Rightarrow f={\mu }_k(F+Mg)\cos \theta$

Hence, option $\left(b\right)$ is correct.