$A$ bob of mass $m$ is hanging from a pulley inside a car by a string. The other end of the string is held by a person standing in the car. The car is moving with a constant horizontal acceleration '$a$' as shown in the figure. The other end of the string is pulled with a constant acceleration '$a$' vertically downward. The tension in the string is equal to-

The tension in the string connected between the two blocks is ......... $N$.

For the system shown in the figure,$m_1 > m_2 > m_3 > m_4$. Initially,the system is at rest in equilibrium. If the string joining $m_4$ and the ground is cut,then just after the string is cut:
Statement $I$: $m_1$,$m_2$,and $m_3$ remain stationary.
Statement $II$: The value of acceleration of all the $4$ blocks can be determined.
Statement $III$: Only $m_4$ remains stationary.
Statement $IV$: Only $m_4$ accelerates.
Statement $V$: All the four blocks remain stationary.
Now,choose the correct option.

$A$ block of mass $m$ is pulled by a force of $40 \, N$ on a smooth horizontal surface as shown in the figure. The tension at the middle of the block is ........... $N$.

In the arrangement shown,the mass $m$ will ascend with an acceleration (Pulley and rope are massless).

The same spring is attached to $2 \ kg, 3 \ kg$ and $1 \ kg$ blocks in three different cases as shown in the figure. If $x_1, x_2$ and $x_3$ are the extensions in the spring in these cases,respectively,find the correct relation between them.