It is easier to roll a barrel than pull it along the road. This statement is

A block of mass $10 \,kg$ is held at rest against a rough vertical wall $[\mu=0.5]$ under the action a force $F$ as shown in figure. The minimum value of $F$ required for it is ............ $N$ $\left(g=10 \,m / s ^2\right)$

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 :

A small block of mass $m$ is projected horizontally with speed $u$ where friction coefficient between block and plane is given by $\mu = cx$, where $x$ is displacement of the block on plane. Find maximum distance covered by the block 

Consider a car moving on a straight road with a speed of $100\, m/s$. The distance at which car can be stopped, is ........ $m$. $[\mu_k = 0.5]$

What is rolling friction ? Write laws of rolling friction. Define coefficient of rolling friction.