Which of the following is a self adjusting force?

Consider a car moving along a straight horizontal road with a speed of $72\, km/h$. If the coefficient of kinetic friction between the tyres and the road is $0.5,$ the shortest distance in which the car can be stopped is ........ $m$ .$[g = 10\,m{s^{ - 2}}]$

A uniform wooden stick of mass $1.6 \mathrm{~kg}$ and length $l$ rests in an inclined manner on a smooth, vertical wall of height $h( < l)$ such that a small portion of the stick extends beyond the wall. The reaction force of the wall on the stick is perpendicular to the stick. The stick makes an angle of $30^{\circ}$ with the wall and the bottom of the stick is on a rough focr. The reaction of the wall on the stick is equal in magnitude to the reaction of the floor on the st $ck$. The ratio $h / l$ and the frictional force $f$ at the bottom of the stick are $\left(g=10 \mathrm{~m} \mathrm{~s}^{-2}\right)$

A block of mass $10\, kg$ starts sliding on a surface with an initial velocity of $9.8\, ms ^{-1}$. The coefficient of friction between the surface and bock is $0.5$. The distance covered by the block before coming to rest is: [use $g =9.8\, ms ^{-2}$ ].........$m$

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

Which one of the following statements is correct