Discuss briefly Galileo's ideas about motion.

Find the retardation with which a train moving at $108 \mathrm{km}/\mathrm{hr}$ is brought to rest in $12$ seconds.

Describe Galileo's experiment. What was the result of this experiment ?

A moving body comes to stop without an application of force. Comment.

A body moves with constant velocity of $20 \mathrm{m} {\mathrm{s}}^{-1}$. The mass of body is $2 \mathrm{kg}$. The unbalanced force acting on the body is _____ $\mathrm{N}$.

Give scientific reasons.
Even though the magnitude of action force and reaction force are equal and their directions are opposite, their effects do not get cancelled.

Define Newton's first law and Inertia.

State Newton's first law of motion.