How much momentum will a dumbbell of mass $10 \, kg$ transfer to the floor,if it falls from a height of $0.8 \, m$? Take acceleration due to gravity as $10 \, m s^{-2}$.

Two balls of the same size but of different materials,rubber and iron,are kept on the smooth floor of a moving train. The brakes are applied suddenly to stop the train. Will the balls start rolling? If so,in which direction? Will they move with the same speed? Give reasons for your answer.

Why is it advised to tie luggage with a rope on the roof of buses?

$(a)$ $(i)$ Define momentum. State its $SI$ unit.
$(ii)$ An object of mass $50 \ kg$ is accelerated uniformly from a velocity of $4 \ m/s$ to $8 \ m/s$ in $8 \ s$. Find the magnitude of the force exerted on the object.
$(b)$ State Newton's first law of motion.

Which Newton's law of motion is applied in the flight of a bird?

$(a)$ When a motorcar makes a sharp turn at a high speed,we tend to get thrown to one side. Why?
$(b)$ State Newton's first and third law of motion.
$(c)$ $A$ force of $5 \ N$ gives a body of mass $m$ an acceleration of $10 \ m \ s^{-2}$. Calculate the mass of the body in grams.