$10\, kg$ block is placed as shown, if $F = 50$ newton find friction force ............ $N$

A child weighing $25 \,kg$ slides down a rope hanging from a branch of a tall tree. If the force of friction acting against him is $200 \,N$, the acceleration of child is ........... $m / s^2$ $\left(g=10 \,m / s ^2\right)$

A car accelerates on a horizontal road due to force exerted by

A horizontal force of $40\,N$ is applied to a $5\, kg$ block which is at rest on the horizontal surface. If the coefficient of kinetic friction is $0.4$, then the acceleration of the block is ........ $m/s^2$ $(g = 10 \,m/s^2)$

Given below are two statements:

$Statement$ $(I)$ : The limiting force of static friction depends on the area of contact and independent of materials.

$Statement$ $(II)$ : The limiting force of kinetic friction is independent of the area of contact and depends on materials.

In the light of the above statements, choose the most appropriate answer from the options given below:

A heavy box of mass $50 \mathrm{~kg}$ is moving on a horizontal surface. If co-efficient of kinetic friction between the box and horizontal surface is $0.3$ then force of kinetic friction is :