Block $A$ of mass $100 \ kg$ is kept above another block $B$ of mass $300 \ kg$. Block $A$ is tied to the wall $C$ with a horizontal string. The coefficient of friction between $A$ and $B$ is $0.35$ and that between $B$ and the horizontal surface is $0.5$. Find the horizontal force $P$ necessary to move the block $B$. (in $N$)

Two blocks $(A)$ of $2\,kg$ and $(B)$ of $5\,kg$ rest one over the other on a smooth horizontal plane. The coefficient of static and dynamic friction between $(A)$ and $(B)$ is the same and equal to $0.60$. Find the maximum horizontal force that can be applied to $(B)$ such that both $(A)$ and $(B)$ do not have any relative motion. $(g = 10\,m/s^2)$

As shown in the figure, block $m$ and wedge $M$ move together with a horizontal acceleration of $20\, m/s^2$. Given $m = 1\, kg$, $\mu = 0.6$ (between $m$ and $M$) and $g = 10\, m/s^2$. Choose the $\text{CORRECT}$ alternative:

$A$ block $A$ of mass $100\, kg$ rests on another block $B$ of mass $200\, kg$ and is tied to a wall as shown in the figure. The coefficient of friction between $A$ and $B$ is $0.2$ and that between $B$ and the ground is $0.3$. The minimum force $F$ required to move the block $B$ is........ $N$. $(g = 10\, m/s^2)$

Block $A$ of mass $3 \ kg$ rests on another block $B$ of mass $7 \ kg$. The coefficient of friction between $A$ and $B$ is $0.4$, while the coefficient of friction between $B$ and the horizontal floor on which $B$ rests is $0.55$. Find the force of friction between $A$ and $B$ when a horizontal force of $50 \ N$ is applied on block $B$. (Use $g = 10 \ m/s^2$) (in $N$)

$A$ block of mass $1\, kg$ lies on a horizontal surface in a truck. The coefficient of static friction between the block and the surface is $0.6$. If the acceleration of the truck is $5\, m/s^2$,the frictional force acting on the block is ........ $N$.