Which force act on body first action or reaction ?

In the system shown in the adjoining figure, the tension $T_2$ is

A car is moving on an overbridge of radius $R$ with a constant speed $v$. As the car is descending on the overbridge from point $B$ to $C,$ the normal reaction on it due to bridge

A mass of $100\,kg$ is moved with uniform velocity under the influence of force $F$, then the force acting on the beam due to string connected to the ceiling ............ $N$

A rope of length $5\,m$ is kept on frictionless surface and a force of $5\,N$ is applied to one of its end. Find tension in the rope at $1\,m $ from this end ......... $N$

A mass of $10 \,kg$ is suspended vertically by a rope of length $5 \,m$ from the roof. A force of $30 \,N$ is applied at the middle point of rope in horizontal direction. The angle made by upper half of the rope with vertical is $\theta=\tan ^{-1}\left(x \times 10^{-1}\right)$. The value of $x$ is ................

$\text { (Given } g =10 \,m / s ^{2} \text { ) }$