Can there be displacement of an object in the absence of any force acting on it? Think. Discuss this question with your friends and teacher.

Two similar trucks are moving with the same velocity on a road. One of them is loaded while the other is empty. Which of the two will require a larger force to stop it?

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

Define Newton's first law and Inertia.

Newton's laws are universal.

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.

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 _____ $\mathrm{N}$.