$A$ $150\, g$ tennis ball coming at a speed of $40\, m/s$ is hit straight back by a bat to a speed of $60\, m/s$. The magnitude of the average force $F$ on the ball,when it is in contact for $5\, ms$,is ........... $N$.

$A$ body of $2\, kg$ has an initial speed of $5\, ms^{-1}$. $A$ force acts on it for some time in the direction of motion. The force-time graph is shown in the figure. Find the final speed of the body in $ms^{-1}$.

$A$ stream of glass beads, each with a mass of $15 \ g$, comes out of a horizontal tube at a rate of $100 \ \text{beads per second}$. The beads fall a distance of $5 \ m$ to a balance pan and bounce back to their original height. How much mass (in $kg$) must be placed in the other pan of the balance to keep the pointer at zero?

The force-time $(F-t)$ curve of a particle executing linear motion is as shown in the figure. The momentum acquired by the particle in the time interval from $0$ to $8 \ s$ will be ........... $N-s$.

What is impulse of force? Write its unit and dimension.

$A$ ball of mass $0.1 \, kg$ coming with a speed of $30 \, m/s$ strikes a bat and returns in the opposite direction with a speed of $40 \, m/s$. Calculate the impulse. (Take the final velocity as positive.)