What is Free body diagram ?

Three blocks of masses $2 \,kg, 3 \,kg$ and $5\, kg$ are connected to each other with light string and are then placed on a frictionless surface as shown in the figure. The system is pulled by a force $F = 10N,$ then tension ${T_1} = $  .......... $N$ 

A mass of $10\,kg$ is suspended vertically by a rope from the roof. When a horizontal force is applied on the rope at some point, the rope deviated at an angle of $45^o$ at the roof point. If the suspended mass is at equilibrium, the magnitude of the force applied is ..........  $N$ $(g = 10\,ms^{-2})$ 

The ends of a rope are held by two men who pulls on it with equal and opposite forces of  magnitude $F$ each. Then the tension in the rope is 

A man is pulling on a rope attached to a block on a smooth horizontal table. The tension in the rope will be the same at all points

A block of mass $M$ is pulled along a horizontal frictionless surface by a rope of mass $M / 2$. If a force $2 Mg$ is applied at one end of the rope, the force which the rope exerts on the block is -