Block $A$ of mass $2 \, kg$ is placed over block $B$ of mass $8 \, kg$. The combination is placed over a rough horizontal surface. The coefficient of friction between block $B$ and the floor is $0.5$. The coefficient of friction between blocks $A$ and $B$ is $0.4$. A horizontal force of $10 \, N$ is applied on block $B$. Find the force of friction between blocks $A$ and $B$. (Take $g = 10 \, ms^{-2}$)

$A$ block $A$ of mass $4\, kg$ is placed on another block $B$ of mass $5\, kg$,and the block $B$ rests on a smooth horizontal table. If the minimum force that can be applied on $A$ so that both the blocks move together is $12\, N$,the maximum force that can be applied to $B$ for the blocks to move together will be ....... $N$.

Consider the system shown below. $A$ horizontal force $F$ is applied to a block $X$ of mass $8 \,kg$,such that the block $Y$ of mass $2 \,kg$ adjacent to it does not slip downwards under gravity. There is no friction between the horizontal plane and the base of the block $X$. The coefficient of friction between the surfaces of blocks $X$ and $Y$ is $0.5$. The minimum value of $F$ is ............ $N$ (take acceleration due to gravity to be $10 \,ms^{-2}$).

The value of $\theta$ is increased gradually from $\theta = 0$. At $\theta = \tan^{-1}(1/2)$,both blocks just start slipping. Then the value of $\mu_2$ is: $(g = 10 \ m/s^2)$

Three blocks $A$,$B$,and $C$ of equal mass $m$ are placed on a smooth surface as shown. The coefficient of friction between any two blocks $A$,$B$,and $C$ is $\mu$. The maximum value of mass $M$ of block $D$ such that blocks $A$,$B$,and $C$ move without slipping over each other is:

Initially,the whole system is at rest. Now,a force of $62 \ N$ is applied on block $B$ as shown in the figure. Find the time taken by block $A$ to fall off block $B$.