In the figure,the position-time graph of a particle of mass $0.1\, kg$ is shown. The impulse at $t = 2\, s$ is ......... $kg\, m/s$.

$A$ ball of mass $50 \,g$ is dropped from a height of $20 \,m$. $A$ boy on the ground hits the ball vertically upwards with a bat with an average force of $200 \,N$,so that it attains a vertical height of $45 \,m$. The time for which the ball remains in contact with the bat is ........... of a second. [Take $g = 10 \,m/s^2$]

$A$ ball of mass $150\,g$ starts moving with an acceleration of $20\,m/s^2$. When hit by a force,which acts on it for $0.1\,s$. The impulsive force is ........ $N-s$.

$A$ body of mass $m_1$ exerts a force on another body of mass $m_2$. If the magnitude of acceleration of $m_2$ is $a_2$,then the magnitude of the acceleration of $m_1$ is (considering only two bodies in space).

The dimensions of impulse are equal to that of

$A$ block of mass $2 \ kg$ moves freely along the $x$-axis. It is at rest at $t = 0$. The force $F(t)$ acting on the block varies with time $t$ as shown in the figure. What is the kinetic energy of the block after $4.5 \ s$ (in $J$)?