Inertial frame of reference

Definition

An inertial frame of reference is a frame of reference in which objects not acted upon by forces move in straight lines at constant speeds. It follows Newton's first law of motion, where no acceleration occurs unless acted upon by an external force.

5 Must Know Facts For Your Next Test

1. Inertial frames are crucial for applying Newton's laws of motion accurately.
2. Within an inertial frame, the law of inertia holds true: objects maintain their state of rest or uniform motion unless acted upon by a net force.
3. Einstein's theory of special relativity assumes that the laws of physics are the same in all inertial frames.
4. Non-inertial frames involve fictitious forces (like centrifugal and Coriolis forces) to account for observed accelerations.
5. A common example of an inertial frame is a spaceship moving at constant velocity far from any gravitational fields.

Review Questions

• Why are Newton's laws only strictly valid in inertial frames?
• How does Einstein’s theory of special relativity utilize the concept of an inertial frame?
• What distinguishes an inertial frame from a non-inertial frame?

Related terms

Newton's First Law:

An object remains at rest or in uniform motion unless acted upon by a net external force.

Non-Inertial Frame: A frame of reference that is accelerating or rotating, where fictitious forces must be introduced to explain motions.

Special Relativity: Einstein’s theory stating that the laws of physics are invariant in all inertial frames and that the speed of light is constant regardless of the observer's motion.