# What forces must be considered in non-inertial rotating reference frames?

• ergonomics
In summary, when dealing with non-inertial rotating reference frames, it is necessary to take into account real forces such as the centripetal force, rather than just the forces that can be observed within the frame. This is because objects in a rotating frame appear to be at rest, and thus the centripetal force must be replaced with the centrifugal force when using Newton's laws. However, it is important to note that the centripetal force is not a separate type of force, but rather a force that acts towards the center of rotation. In a rotating frame, both real and fictitious forces must be considered in order to accurately apply Newton's laws.
ergonomics
dealing with non-inertial rotating reference frames, real forces such as the centripetal force need to be taken into account,or only the forces that can be really observed within the frame?

because from the perspective of the rotating frame, objects should be at rest. it only appears logical to replace the centripetal force with the centrifugal force when dealing in rotating frames.

Real forces always count. "Real" forces have agents as opposed to "fictitious" inertial forces that are artifacts of using a noninertial frame of reference.

Note: "centripetal" force just means a force that acts toward the center (or the net force acting toward the center)--it's not a separate kind of force.

Example: Imagine a spinning turntable on which a small block sits. The block spins along with the turntable. From an inertial frame, the block is centripetally accelerated; the centripetal force is the friction between turntable and block.

From the rotating frame that very real friction force still acts, but now the acceleration is zero: In addition to the real friction force, one needs to add the "fictitious" centrifugal force in order to use Newton's laws.

I would like to clarify that both the centripetal force and the centrifugal force need to be taken into account when dealing with non-inertial rotating reference frames. In such frames, objects appear to be at rest but are actually experiencing a centripetal force that keeps them in circular motion. This centripetal force is a real force and must be considered in any analysis of the system. The centrifugal force, on the other hand, is a fictitious force that arises due to the inertia of the object in motion. It is a result of the frame of reference and does not actually act on the object. Therefore, while the centrifugal force may seem logical to replace the centripetal force in a rotating frame, it is important to understand that both forces play a role in the dynamics of the system. Only considering the forces that can be observed within the frame may lead to incorrect conclusions and inaccurate predictions. It is essential to take into account all real forces, including the centripetal force, in order to fully understand and accurately analyze systems in non-inertial rotating reference frames.

## 1. What is a non-inertial reference frame?

A non-inertial reference frame is a coordinate system that is accelerating or rotating. This means that the laws of physics do not hold true in this frame and objects within it may experience apparent forces that do not exist in an inertial reference frame.

## 2. How is a non-inertial reference frame different from an inertial reference frame?

An inertial reference frame is a coordinate system that is not accelerating or rotating, and in which the laws of physics hold true. In contrast, a non-inertial reference frame is accelerating or rotating, leading to the effects of apparent forces and the violation of certain physical laws.

## 3. What are some examples of non-inertial reference frames?

Examples of non-inertial reference frames include a car accelerating, a rotating carousel, or a plane turning in the air. Any frame that is accelerating or rotating, even if it is at a constant speed, can be considered a non-inertial reference frame.

## 4. How do non-inertial reference frames affect the measurement of motion?

In a non-inertial reference frame, the concepts of velocity and acceleration become more complex. This is because apparent forces, such as centrifugal force, can affect the measurement of motion. Additionally, the laws of motion, such as Newton's laws, may not hold true in a non-inertial reference frame.

## 5. Why are non-inertial reference frames important in physics?

Non-inertial reference frames are important in physics because they allow us to understand and analyze the effects of acceleration and rotation on objects. They also help us to better understand the limitations of our physical laws and how they may change in different reference frames.

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