The arrangement of a two-block system is as shown. Assuming the surfaces to be frictionless,the net force acting on the $1 \, kg$ and $2 \, kg$ blocks are,respectively:

$A$ block $A$ of mass $7 \, kg$ is placed on a frictionless table. $A$ thread tied to it passes over a frictionless pulley and carries a body $B$ of mass $3 \, kg$ at the other end. The acceleration of the system is .......... $m \, s^{-2}$ (given $g = 10 \, m \, s^{-2}$).

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.

$A$ rope of length $10 \, m$ and linear density $0.5 \, kg/m$ is lying lengthwise on a smooth horizontal floor. It is pulled by a force of $25 \, N$. The tension in the rope at a point $8 \, m$ away from the point of application is ....... $N$

$A$ force $F = 10t$ acts on a block of mass $10 \, kg$ as shown in the figure. Find the time $t$ when the block loses contact with the surface.

The figure shows four blocks that are being pulled along a smooth horizontal surface. The masses of the blocks and the tension in one string are given. The pulling force $F$ is ............ $N$.