Reference Frames: Inertial vs. Non-Inertial
In physics, reference frames are essential for describing the position and motion of objects.
Reference frame
A reference frame is a coordinate system that allows us to measure the position, velocity, and time of events.
Inertial Reference Frames
Inertial reference frame
An inertial reference frame is one where Newton’s first law holds true: an object at rest stays at rest, and an object in motion continues in a straight line at constant speed unless acted upon by a force.
Inertial frames are either at rest or moving with constant velocity.
Non-Inertial Reference Frames
Non-inertial reference frame
A non-inertial reference frame is one that is accelerating.
In these frames, objects appear to experience fictitious forces, such as the sensation of being pushed back in a car that accelerates forward.Note
Non-inertial frames require corrections for these fictitious forces to accurately describe motion.
Identifying Reference Frames
Consider these scenarios:
- A train moving at constant speed on a straight track is an inertial frame.
- A car accelerating around a curve is a non-inertial frame.
Which of the following are inertial frames?
- A satellite orbiting Earth
- A car moving at constant speed on a straight road
- A spinning merry-go-round
Galilean Transformations: Relating Two Reference Frames
- Galilean transformations provide a mathematical framework to relate the coordinates of an event in one inertial frame to another.
- These transformations assume that time is absolute and the same for all observers.
The Basic Equations
Consider two reference frames, $S$ and $S′$:
- $S$ is stationary.
- $S′$ moves with a constant velocity $v$ relative to $S$ along the x-axis.
