Name the physical quantity that measures inertia. State its $SI$ unit.

Derive the unit of force using the second law of motion. $A$ force of $5 \, N$ produces an acceleration of $8 \, m s^{-2}$ on a mass $m_1$ and an acceleration of $24 \, m s^{-2}$ on a mass $m_2$. What acceleration would the same force provide if both the masses are tied together (in $, m s^{-2}$)?

$A$ horse continues to apply a force in order to move a cart with a constant speed. Explain why?

$(i)$ 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.

State Newton's second law of motion.

$(a)$ Define momentum of a body.
$(b)$ $A$ ball is thrown vertically upward. What is its momentum at the highest point?
$(c)$ State the law of conservation of momentum.