Swimming is possible on account of

The average force necessary to stop a hammer having momentum $50 \ N-s$ in $0.25 \ s$ is ...... $N$.

$A$ force of $10 \, N$ acts on a body of mass $20 \, kg$ for $10 \, s$. The change in its momentum is ........... $kg \cdot m/s$.

Two billiard balls each of mass $0.05\; kg$ moving in opposite directions with speed $6\; m/s$ collide and rebound with the same speed. What is the impulse imparted to each ball due to the other (in $; Ns$)?

$A$ mass of $1 \ kg$ is suspended by a string $A$. Another string $C$ is connected to its lower end (see figure). If a sudden jerk is given to $C$,then

$A$ particle moves in the $x-y$ plane under the action of a force $\overrightarrow{F}$ such that the value of its linear momentum $\overrightarrow{P}$ at any time $t$ is $P_x = 2\cos t$ and $P_y = 2\sin t$. The angle $\theta$ between $\overrightarrow{F}$ and $\overrightarrow{P}$ at a given time $t$ will be $\theta = $ ........... $^o$.