In Newtonian mechanics,which parameter is changed by the application of an external force?

Why does a cricket player move their hands backward while catching a fast-moving ball?

An object of mass $m \, kg$ with speed $v \, m/s$ strikes a wall at an angle $\theta$ with the normal and rebounds at the same speed and same angle. The magnitude of the change in momentum of the object will be

When the speed of a moving body is doubled:

$A$ machine gun can fire $200$ bullets $\min^{-1}$. If $35 \ g$ bullets are fired at a speed of $750 \ m \ s^{-1}$, the average force exerted by the gun on the bullets is, (in $N$)

$A$ uniformly moving cricket ball is turned back by hitting it with a bat for a very short time interval. Show the variation of its acceleration with time (Take acceleration in the backward direction as positive).