$A$ block of mass $2 \, kg$ is kept on the floor. The coefficient of static friction is $0.4$. If a force $F$ of $2.5 \, N$ is applied on the block as shown in the figure,the frictional force between the block and the floor will be ........ $N$.

If ${\mu _s}$,${\mu _k}$,and ${\mu _r}$ are coefficients of static friction,sliding (kinetic) friction,and rolling friction respectively,then:

$A$ body of mass $1 \, kg$ rests on a horizontal floor with which it has a coefficient of static friction $\frac{1}{\sqrt{3}}$. It is desired to make the body move by applying the minimum possible force $F \, N$. The value of $F$ will be (Nearest Integer). [Take $g = 10 \, m s^{-2}$]

Which of the following forces does not depend on the velocity: the frictional force between the contact surfaces of two solids or the viscous force?

What is the maximum acceleration of a train such that a $50 \ kg$ box lying on its floor remains stationary (in $m \ s^{-2}$)? (Given: Coefficient of static friction between the box and the train's floor is $0.3$ and $g = 10 \ m \ s^{-2}$)

$A$ heavy body of mass $25 \ kg$ is to be dragged along a horizontal plane $\left( \mu = \frac{1}{\sqrt{3}} \right)$. The least force required is ........ $kgf$.