$A$ body is moving with a uniform velocity of $2 \, m/s$ on a rough level surface. The frictional force on it is $10 \, N$. If the body moves with a velocity of $4 \, m/s$,the force of friction will be ........ $N$.

$A$ force $\vec{F}=\hat{i}+4 \hat{j}$ acts on the block shown in the figure. The force of friction acting on the block is (take $g=10 \, m/s^2$)

$A$ block of mass $40 \,kg$ slides over a surface,when a mass of $4 \,kg$ is suspended through an inextensible massless string passing over a frictionless pulley as shown below. The coefficient of kinetic friction between the surface and the block is $0.02$. The acceleration of the block is ............ $m/s^2$. (Given $g = 10 \,m/s^2$.)

$A$ block of a certain mass is placed on a rough floor. The coefficients of static and kinetic friction between the block and the floor are $0.4$ and $0.25$ respectively. $A$ constant horizontal force $F = 20 \text{ N}$ acts on it so that the velocity of the block varies with time according to the following graph. The mass of the block is nearly (Take $g = 10 \text{ m/s}^2$): (in $\text{ kg}$)

$A$ rectangular block has a square base measuring $a \times a$ and its height is $h$. It moves on a horizontal surface in a direction perpendicular to one of the edges. The coefficient of friction is $\mu$. It will topple if

Which of the following is correct when a person walks on a rough surface?