# What is the principle of Physical Independence of Motions?

## Principle of Physical Independence of Motions

Motion of projectile is two-dimensional motion in a vertical plane.

It can be resolved in two motions along horizontal & vertical direction These two motions are independent of each other.

This is called the principle of physical independence of motions.

At any instant velocity of projectile has two components :

(i) Horizontal Component : No acc. along horizontal $\left(\mathrm{a}_{\mathrm{x}}=0\right)$ so velocity along horizontal remains unchanged throughout the flight.

Horizontal motion is a uniform motion.

(ii) Vertical Component: Acceleration due to gravity in a downward direction will change the vertical component of velocity continuously throughout the motion.

Vertical motion is uniformly accelerated motion.