In the arrangement shown in fig. the ends $P$ and $Q$ of an unstretchable string move downwards with uniform speed $U$. Pulleys $A$ and $B$ are fixed. Mass $M$ moves upwards with a speed.

If pulleys shown in the diagram are smooth and massless and $a_1$ and $a_2$ are acceleration of blocks of mass $4 \,kg$ and $8 \,kg$ respectively, then

In the given figure acceleration of wedge $'A'$ is $10\ m/s^2$ along the inclined plane. (There is no friction between $A$ $\&$ $B$ and $A$ $\&$ fixed inclined plane.) Then acceleration of block $'B'$ will ............ $m/s^2$

Find velocity of block ' $B$ ' at the instant shown in figure $........\,m/s$

Three blocks of masses $m_1=4 \,kg , m_2=2 \,kg , m_3=4 \,kg$ are connected with ideal strings passing over a smooth. massless pulley as shown in figure. The acceleration of blocks will be ......... $m / s ^2$ $\left(g=10 \,m / s ^2\right)$

Two blocks of same mass $(4\ kg)$ are placed according to diagram. Initial velocities of bodies are $4\ m/s$ and $2\ m/s$ and the string is taut. Find the impulse on $4\ kg$ when the string again becomes taut  .......... $N-s$