$(i)$ Define momentum. Write its $SI$ unit.
$(ii)$ How much momentum will an object of mass $10 \ kg$ transfer to the floor if it falls from a height of $5 \ m$? $(g = 10 \ m \ s^{-2})$
$(iii)$ Explain how a karate player can break a pile of tiles with a single blow of his hand.

$(100 \ kg \ m \ s^{-1})$ $(i)$ The product of mass and velocity of an object is known as its momentum. The $SI$ unit of momentum is $kg \ m \ s^{-1}$.
$(ii)$ Mass of the object, $m = 10 \ kg$.
Height, $h = 5 \ m$.
Acceleration due to gravity, $g = 10 \ m \ s^{-2}$.
Initial velocity of the object, $u = 0$.
From the third equation of motion, $v^2 - u^2 = 2gh$.
$v^2 - 0^2 = 2 \times 10 \times 5$.
$v^2 = 100$.
$v = 10 \ m \ s^{-1}$.
Momentum transferred to the floor = Change in momentum = $mv - mu$.
$= (10 \times 10) - (10 \times 0) = 100 \ kg \ m \ s^{-1}$.
$(iii)$ A karate player moves his hand at a very high speed to strike the tiles. By doing this, the large momentum of his hand is reduced to zero in a very short interval of time. According to Newton's second law, $F = \frac{\Delta p}{\Delta t}$, since the time interval $\Delta t$ is extremely small, the force $F$ exerted on the tiles becomes very large, which is sufficient to break them.