If the normal force is doubled,the coefficient of friction is

What can be inferred from the relation $f_S \leqslant \mu_S N$?

Which of the following is true about the coefficient of static friction $(\mu_s)$ and the coefficient of kinetic friction $(\mu_k)$?

As shown in the figure, a block of mass $10 \ kg$ lying on a horizontal surface is pulled by a force $F$ acting at an angle $30^{\circ}$ with the horizontal. For $\mu_{s} = 0.25$, the block will just start to move for the value of $F$: [Given $g = 10 \ ms^{-2}$] (in $N$)

The maximum force of friction is called:

$A$ block of mass $2\,kg$ is at rest on a floor. The coefficient of static friction between the block and the floor is $0.54$. $A$ horizontal force of $2.8\,N$ is applied to the block. What will be the frictional force between the block and the floor (in $.8$)? $(g = 10\,m/s^2)$