Difficulty with non-inertial frames

In summary, the conversation revolves around the difficulty of processing non-inertial frame homework problems and the struggle to combine inertial and non-inertial reference frames mathematically. The example of a kid on a water slide is used to illustrate the issue and the solution involves using acceleration components and the ratio of acceleration in the non-inertial and inertial frames. The person is seeking suggestions for improving their ability to solve these types of problems and is advised to have a strong understanding of rotation and angular velocity concepts.
  • #1
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I seem to be having some trouble processing non-inertial frame homework problems. I hear that sometimes attempting to explain the problem helps with the understanding so here goes. I don't think I have any difficulty visualizing the problems. Creating free body diagrams (FBD) from the non-inertial (NI) reference frame are pretty easy using fictitious forces. And I know I'm o.k. at FBD's from inertial (I) reference frames. But I seem unable to combine them properly mathematically to obtain a correct final solution. A good example:

A kid is on a water slide riding high on a horizontal curve raising her head to look past her toes. With the given radius and velocity I have no trouble obtaining centripetal accel. and the radial force. Knowing that her neck muscles exert a given force while at rest (lying down) to lift her head normally I need to determine the force req'd to look past her toes on the slide. My first attempt used the assumption that I needed to determine the mass of her head and multiply that by the centripetal accel. to find the force req'd to lift her head at that velocity against the "centrifugal" force. It seems I didn't need the mass and I should have used only accel. components. And I foolishly assumed gravity wasn't an issue. I also think I forgot about basic vector addition in solving, arrrgh! Finally, the solution used the ratio of accel. of -NI- vs. -I- to determine a multiple for the original force to lift her head to obtain the final answer. I'm not sure I would have thought of that.

I suppose my main questions are; What suggestions can anyone give as to a good course of action to better solve these types of problems? And, if no suggestions is it better to just continue to plug and chug a lot of these till I get the hang of it.
 
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  • #2
Welcome to PF.
YOUR PROBLEM DOES NOT LIE IN NON INERTIAL FRAMES BUT RATHER THE ABILITY TO EXPRESS IT MATHEMATICALLY.ROTATION AND CONCEPTS OF ANGULAR VELOCITY ARE VERY IMPORTANT COURSE AND BEFORE YOU PROCEED TO SOLVE ANY NUMERICALS ALWAYS HAVE THE THEORY WITH YA.

http://www.mel.nist.gov/div822/basic.htm
 
  • #3


I can assure you that difficulty with non-inertial frames is a common struggle for many students. The concept of non-inertial frames can be challenging to grasp, but with practice and a thorough understanding of the underlying principles, you will be able to solve these problems successfully.

Firstly, it is essential to have a solid understanding of the difference between inertial and non-inertial frames. In an inertial frame, an object will remain at rest or continue moving at a constant velocity unless acted upon by an external force. In contrast, in a non-inertial frame, an object may appear to accelerate even if no external forces are acting on it due to the frame's acceleration.

To solve problems involving non-inertial frames, it is crucial to correctly identify and account for all forces acting on the object in the frame. As you mentioned, fictitious forces are often used to account for the acceleration of the frame. It is essential to understand how these forces arise and how to correctly incorporate them into your calculations.

In the example you provided, it is crucial to consider all forces acting on the kid, including the fictitious centrifugal force, the force exerted by the neck muscles, and the force of gravity. It is also essential to understand how these forces are related and how they contribute to the overall motion of the object.

My suggestion would be to practice solving problems involving non-inertial frames, starting with simpler ones and gradually increasing the complexity. It can also be helpful to work with a tutor or a study group to discuss and compare solutions. Additionally, make sure to thoroughly review the concepts and principles behind non-inertial frames to ensure a solid understanding.

In summary, solving problems involving non-inertial frames can be challenging, but with practice and a thorough understanding of the underlying principles, you will be able to master it. Keep practicing and don't be discouraged by mistakes – they are an essential part of the learning process. Best of luck!
 

1. What is a non-inertial frame?

A non-inertial frame is a reference frame in which Newton's laws of motion do not hold true. In other words, objects moving in this frame experience fictitious forces that are not present in an inertial frame.

2. What causes difficulty with non-inertial frames?

The difficulty with non-inertial frames arises due to the presence of fictitious forces. These forces can complicate the analysis of motion and make it more challenging to accurately predict the behavior of objects.

3. How do you identify a non-inertial frame?

A non-inertial frame can be identified by observing if objects in the frame appear to accelerate without any external forces acting on them. This is a sign that fictitious forces are present.

4. How can you account for non-inertial frames in scientific experiments?

To account for non-inertial frames in experiments, scientists often use coordinate transformations or adjust for the fictitious forces in their calculations. This allows for more accurate results and a better understanding of the observed phenomena.

5. Is it possible to completely eliminate the effects of non-inertial frames?

No, it is not possible to completely eliminate the effects of non-inertial frames. However, by properly accounting for them, scientists can minimize their impact on the accuracy of their experiments and calculations.

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