Two masses of $4\, kg$ and $5 \,kg$ are connected by a string passing through a frictionless pulley and are kept on a frictionless table as shown in the figure. The acceleration of the $5\, kg$ mass is ........... $m/s^2$.

Two blocks of masses $m$ and $2m$ kept on a frictionless horizontal surface are connected by a massless string. Two horizontal forces $F_1 = (4.2t) \text{ N}$ and $F_2 = (7.5t) \text{ N}$,where '$t$' is time in seconds,are acting on the system as shown in the figure. The time at which the tension in the string between the two blocks becomes $10.6 \text{ N}$ is $t$ seconds.

Two particles each of mass $m$ are moving in horizontal circles with the same angular speed $\omega$. If both strings are of the same length $l$,find the ratio of tension in the strings $\frac{T_1}{T_2}$.

$A$ rope of mass $5 \,kg$ is moving vertically in a vertical position with an upward force of $100 \,N$ acting at the upper end and a downward force of $70 \,N$ acting at the lower end. The tension at the midpoint of the rope is ......... $N$.

$A$ body of mass $2 \, kg$ moves under a force of $(2 \hat{i} + 3 \hat{j} + 5 \hat{k}) \, N$. It starts from rest and was at the origin initially. After $4 \, s$,its new coordinates are $(8, b, 20)$. The value of $b$ is ........ . (Round off to the Nearest Integer)

$A$ block $P$ of mass $M_P$ is in contact with another block $Q$ of mass $M_Q$ as shown in the figure and they are placed on a smooth floor. Find the force on block $Q$.