A force $f$ is acting on a block of mass $m$. Coefficient of friction between block and surface is $\mu$. The block can be pulled along the surface if :-
$\tan \theta \ge \mu $
$\cot \theta \ge \mu $
$\tan \frac{\theta }{2} \ge \mu $
$\cot \frac{\theta }{2} \ge \mu $
The coefficient of friction $\mu $ and the angle of friction $\lambda $ are related as
A coin placed on a rotating table just slips when it is placed at a distance of $1\,cm$ from the center. If the angular velocity of the table in halved, it will just slip when placed at a distance of from the centre $............\,cm$
Static friction between two surfaces
In the given figure the acceleration of $M$ is $(g = 10 \,ms^{-2})$
In figure, the coefficient of friction between the floor and the block $B$ is $0.2$ and between blocks $A$ and $B$ is $0.3$. ........ $N$ is the maximum horizontal force $F$ can be applied to the block $B$ so that both blocks move together .