For the free body diagram shown in the figure,four forces are applied in the $x$ and $y$ directions. What additional force must be applied and at what angle with the positive $x$-axis so that the net acceleration of the body is zero?

When a body is stationary,which of the following statements is true?

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:

$A$ book is lying on a table. What is the angle between the normal reaction acting on the book on the table and the weight of the book (in $^\circ$)?

What will be the tension produced in the string $PQ$ for the given system?

$A$ $50 \, kg$ homogeneous smooth sphere rests on a $30^{\circ}$ incline $A$ and bears against a smooth vertical wall $B$. Calculate the contact force at $A$. (Take $g = 10 \, m/s^2$)