$A$ man pushes a box of mass $50\, kg$ with a force of $80\, N$. What will be the acceleration of the box due to this force? What would be the acceleration if the mass were doubled?

An object of mass $2\, kg$ is sliding with a constant velocity of $4\, m\, s^{-1}$ on a frictionless horizontal table. The force required to keep the object moving with the same velocity is (in $, N$)

$(a)$ Define momentum and mention its $SI$ unit.
$(b)$ From the velocity-time graph shown in the figure for a body of mass $5\, kg$,find the force on the body from:
$(i)$ $O$ to $A$ and $(ii)$ $B$ to $C$.
$(c)$ Which would require a greater force: accelerating a $2\, kg$ mass at $5\, m s^{-2}$ or a $4\, kg$ mass at $2\, m s^{-2}$?

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

Write answers to the following:
$(i)$ Mention the direction in which the force of friction acts on a moving body. State its units.
$(ii)$ Name the property of bodies (or objects) to resist a change in their state of rest or of motion. Name the quantity that is a measure of this property.
$(iii)$ Name the physical quantity whose unit is $kg\, m s^{-1}$. Define this quantity.

Which has the highest inertia among solids made of aluminium,steel,and wood of the same shape and same volume?