Inertial Frames of Reference

Newton’s first law is usually considered to be a statement about reference frames. It provides a method for identifying a special type of reference frame: the inertial reference frame. In principle, we can make the net force on a body zero. If its velocity relative to a given frame is constant, then that frame is said to be inertial. So, by defi...

The frame of reference in which Newton's laws are valid is called an inertial frame of reference. The object relative to this frame of reference continues to stay at rest or move with a constant velocity.

Consider a  car in motion. The passenger is moving along with the car relative to the Earth. When the car stops suddenly, the passenger...