A non-inertial frame is a frame of reference that is accelerating relative to an inertial frame.
Understanding Inertial and Non-Inertial Frames
To grasp the concept of a non-inertial frame, it's helpful to first understand what an inertial frame is. An inertial frame is a reference frame in which Newton's laws of motion hold true. In such a frame, an object at rest stays at rest, and an object in motion continues in motion with a constant velocity unless acted upon by a net force.
Key Characteristics of a Non-Inertial Frame
According to the provided reference, a non-inertial frame (also known as an accelerated reference frame) is characterized by the following:
- Acceleration: It undergoes acceleration with respect to an inertial frame. This means its velocity is changing, either in magnitude, direction, or both.
- Non-Zero Acceleration Detection: An accelerometer at rest in a non-inertial frame will typically detect a non-zero acceleration.
Differences Between Inertial and Non-Inertial Frames
| Feature | Inertial Frame | Non-Inertial Frame |
|---|---|---|
| Acceleration | Does not accelerate. | Undergoes acceleration with respect to an inertial frame. |
| Newton's Laws | Newton's Laws of Motion hold true. | Newton's Laws of Motion do not hold true without modification. |
| Accelerometer | An accelerometer at rest reads zero. | An accelerometer at rest reads non-zero. |
Example Scenarios
- Car Acceleration: A car accelerating forward is an example of a non-inertial frame. Passengers in the car feel a force pushing them back into their seats.
- Rotating Carousel: A rotating carousel is also a non-inertial frame. Objects on the carousel experience fictitious forces (like the centrifugal force) that do not arise from direct physical interactions.
- Elevator: An elevator that's accelerating (either going up or down) is considered a non-inertial frame.
Fictitious Forces
In non-inertial frames, fictitious forces (also called inertial forces) appear to act on objects. These are not actual forces, but rather consequences of the frame's acceleration. Examples include:
- Centrifugal Force: Experienced in rotating frames, pushing objects outward from the center of rotation.
- Coriolis Force: Experienced in rotating frames, deflecting moving objects.
- Linear Acceleration Force: Experienced in frames accelerating linearly, like the force felt in an accelerating vehicle.
How to Solve Problems in Non-Inertial Frames
In order to correctly solve physics problems in a non-inertial frame, you must account for the fictitious forces which arise from the frame's acceleration. This can be achieved by adding those fictitious forces in the equations of motion.
Summary
In essence, a non-inertial frame of reference is one that is accelerating relative to an inertial reference frame. This acceleration causes objects within the non-inertial frame to experience fictitious forces. This can be detected by an accelerometer which measures a non-zero acceleration, even if at rest within this frame.
