An inertial frame of reference is a coordinate system in which Newton's laws of motion hold true without the influence of any external forces.
An inertial frame of reference is a coordinate system that is not accelerating, while a non-inertial frame of reference is a coordinate system that is accelerating or rotating. In a non-inertial frame, Newton's laws of motion may not hold true without the inclusion of fictitious forces.
A reference frame is considered inertial if an object at rest in that frame remains at rest and an object in motion maintains a constant velocity in a straight line without any external forces acting on it.
No, an object can only be in one inertial frame of reference at a time. However, the observer can choose different inertial frames of reference to describe the motion of the same object.
Inertial frames of reference provide a consistent and reliable way to measure and describe motion, and they allow for the application of fundamental laws and principles in physics. They are also essential in understanding the relationship between space and time, as described by the theory of relativity.