For the given figure what will be the contact force applied by $6\ kg$ block on $4\ kg$ block ............ $N$

Two blocks of  $7\,\,kg$ and $5\,\,kg$  are connected by a heavy rope of mass $4\,\,kg.$ An upward force of $200\,N$  is applied as shown in the diagram. The tension at the top of heavy rope at point $P$  is ....... $N$ $(g = 10\,\,m/s^2)$

A uniform rope of mass $1.0\, kg$ is connected with a box of mass $2.0\, kg$, which is placed on a smooth horizontal surface. The free end of the rope is pulled horizontally by a force $6\, N$. Find the tension at the midpoint of the rope ....... $N$

Two particle of mass $m$ each are tied at the ends of a light string of length $2 \mathrm{a}$. The whole system is kept on a frictionless horizontal surface with the string held tight so that each mass is at a distance $'a'$ from the center $\mathrm{P}$ (as shown in the figure). Now, the mid-point of the string is pulled vertically upwards with a small but constant force $F$. As a result, the particles move towards each other on the surface. The magnitude of acceleration, when the separation between them becomes $2 \mathrm{x}$ is

A block of mass $8\, kg$ is at rest on a rough inclined plane as shown in figure. The magnitude of net force exerted by the surface on the block will be ......... $N$

A wooden block of mass $2\; kg$ rests on a soft horizontal floor. When an iron cylinder of mass $25\; kg$ is placed on top of the block, the floor yields steadily and the block and the cylinder together go down with an acceleration of $0.1\; m /s^2$. What is the action of the block on the floor $(a)$ before and $(b)$ after the floor yields ? Take $g = 10 \;m /s^2$. Identify the action-reaction pairs in the problem