It is difficult to move a cycle with brakes on because

$A$ stone weighing $1$ kg and sliding on ice with a velocity of $2$ m/s is stopped by friction in $10$ sec. The force of friction (assuming it to be constant) will be ......... $N$.

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

Meena applies the front brakes while riding her bicycle along a flat road. The force that slows her bicycle is provided by the

Two blocks $A$ and $B$ of masses $2 \ kg$ and $4 \ kg$ respectively are kept on a rough horizontal surface. If the same force of $20 \ N$ is applied on each block,then the ratio of the accelerations of the blocks $A$ and $B$ is (Coefficient of kinetic friction between the surface and the blocks is $0.3$ and acceleration due to gravity $= 10 \ m \ s^{-2}$).

If the normal reaction is $R$ and the coefficient of friction is $\mu$,what is the work done against friction in moving a body by a distance $d$ slowly?