In the following figure,the object of mass $m$ is held at rest by a horizontal force $F$ as shown. The force exerted by the string on the block is

$A$ ladder rests against a frictionless vertical wall,with its upper end $6 \, m$ above the ground and the lower end $4 \, m$ away from the wall. The weight of the ladder is $500 \, N$ and its center of gravity ($C$.$G$.) is at $1/3$ of its length from the lower end. The reaction force from the wall will be (in Newton):

Statement-$I$: If three forces $\vec{F}_{1}, \vec{F}_{2}$ and $\vec{F}_{3}$ are represented by three sides of a triangle and $\vec{F}_{1} + \vec{F}_{2} = -\vec{F}_{3}$,then these three forces are concurrent forces and satisfy the condition for equilibrium.
Statement-$II$: $A$ triangle made up of three forces $\vec{F}_{1}, \vec{F}_{2}$ and $\vec{F}_{3}$ as its sides taken in the same order,satisfy the condition for translatory equilibrium.
In the light of the above statements,choose the most appropriate answer from the options given below:

Two equal heavy spheres,each of radius $r$,are in equilibrium within a smooth cup of radius $3r$. The ratio of the reaction between the cup and one sphere to that between the two spheres is:

Write the similarities and differences between contact force and field force.

$A$ 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 deviates at an angle of $45^o$ from the vertical. If the suspended mass is at equilibrium,the magnitude of the force applied is .......... $N$ $(g = 10\,ms^{-2})$.