Question

a block is sliding on a rough horizontal surface. if the contact force on the block is root2 times the frictional force, the coefficient of friction is?

Answer 1

Here the contact force is normal reaction.

so,
$$\begin{gathered} N=\sqrt{2}\times f \\ N=normalreaction \\ f=frictionalforce \\ mg=\sqrt{2}\times \mu \times mg \\ \mu =\frac{1}{\sqrt{2}}. \end{gathered}$$