1. Conceptual Distinction

The article distinguishes two notions often conflated under the single term "centrifugal force":

the inertial (fictitious) centrifugal force, a pseudo-force that exists only in a rotating (non-inertial) reference frame and vanishes upon a change of frame;

the reactive centrifugal force, a genuine Newtonian force arising directly from Newton's third law.

1. Theoretical Basis

For a body to follow a circular trajectory, a constraint (a string, a wall, a spring) must exert a centripetal force on it, directed toward the center. By Newton's third law, the body in turn exerts on that constraint an equal and opposite force, directed outward: this is the reactive centrifugal force. Unlike the inertial force, it holds in any reference frame and manifests physically as tension, compression, or shear within the constraint itself. The two forces share the same magnitude only when the axis of the rotating frame coincides with the center of the trajectory.

1. Applications

The author illustrates this concept with two cases:

A rapidly spinning turbine blade, modeled as a stack of radial layers extending from the axis to the tip. Each layer transmits a reactive centrifugal force to the layer immediately closer to the axis, while simultaneously receiving an elastic centripetal force from the layer farther out. This chain of loading generates the internal tension within the material, a quantity central to mechanical design.

The centrifugal clutch (used in chainsaws, go-karts, and miniature helicopters), in which rotating shoes are initially restrained by a spring, which supplies the centripetal force at low speed. Above a threshold speed, the outer drum takes over this role; the reactive centrifugal force exerted by the shoes against the drum then produces the normal contact force, which is the condition for the friction that engages the drive.

Both cases show how the reactive centrifugal force propagates step by step through a mechanical structure — from one layer to the next in the blade, from a moving part to a fixed part in the clutch — accounting for internal stresses and friction mechanisms without ever invoking a global centrifugal force postulated a priori.

The title might sound simplistic, but I want to say that I recently became interested in returning to physics. To clarify, I'm currently studying social sciences because I really enjoyed philosophy and history, but I was bad at pure mathematics (not so much anymore, I've improved). That's why I chose social sciences, but as a hobby, I love listening to physics. Since I was six, hearing stories about famous physicists and discoveries has fascinated me, and I'd like to return to that world (when I studied physics in high school, I was actually quite good, getting average grades and sometimes 8/10s; I only missed out on a perfect score because of the calculations). How can I immerse myself in physics without getting lost? I'd like a guide to the basics and then to the more difficult topics, or as far as I can go, although I'll start with the easy stuff to warm up. What topics should I cover in an order I can understand?

Hello, I would like to model an experiment in Python:
Rotational motion (mechanical energy): a plate that lowers under the weight of a mass, driving a spinning top, which then drives a gear → Coil + magnet → Capacitor: electrical energy.
However, I’m not sure how to choose the initial conditions, such as the pitch, spring length, etc. Could you please help me figure out how to determine these parameters?

The human body experiences buoyancy because water exerts an upward force that pushes against the body's total weight

Hello everyone:

I have this design for a new type of propulsion system to enable the sought after "Warp-Drive" engine, based in a Photophone I designed initially for recording signals, but it can actually transduce electricity into coherent light waves in general sense. The laser(s) will be placed in the front of the hull pointing forward, like the propeller blades of an aircraft. I expect the laser to transmit the acoustic modulation to the space plasma and "entangle" or ionize symmetrically in a unified electromagnetic field a relatively large volume of space populated by ions, and create such as an electrostatic field that would pull the ship forward. My vision is a spaceship with ionic or chemical back thrusters, and a few lasers in the front ionizing the medium. Once the ship picks up speed and enters the ionized region, the back thruster will expand the matter getting past the horizon events formed right in front of the laser lenses, expanding the bubble backwards. And there you go warp-drive.

I am having many issues with posting this because I had become long ago a dissident of Physics' today's state. For years I used to read many papers and some books. I did not studied Physics but I studied Audio Engineering and worked for some years in radio, and I have a good background in electronics and signal analysis, and I certainly can understand most Physical theories and even most equations. But I do not agree with many postulates and approaches of today's Physics. Simply I think that nowadays theory has become a vast valley of speculative knowledge without too many actual results other than experiments and more experiments, and there is a very generalized subjective hope that from the discovery of a single property of the universe or a single type of energy or "particle" the collective would be able to engineer steadfast a certain engine that uses that special property or particle to do its thing.

In my case I am offering a simple and feasible engineering solution, as simple as must inventions that have worked are. And I can explain it with my own words, just like if you asked an inventor, not a theoretical scientist that will overflood you with knowledge but without practical solutions.

I am posting this here asking for suggestions of what mathematical model(s) and Physics theories you would use to explain what happens when an acoustically modulated laser interference pair excited the plasma in the outer space, if I wanted to explain this to theorists who only say they agree if it sound similar to the rest of their knowledge. Also, I looking to invite people to join me if they wish to participate in the project of creating an engineering venture, to apply for funding programs with several institutions and organizations to research on this specific subject and build the constant-velocity-device or Warp Drive that this can become. I am looking for people for the positions of CEO/foreman, CTO/foreman (or forewoman), mathematicians, physicists, designers, engineers and researchers; I only want to be a researcher. So please DM me if you feel like, aside contributing with the theoretical and mathematical models to study this proposal.

(The diagram shows the recording head I invented first, which is not the propeller but is very similar. Just let's say we are using a negative lens to expand the beam past the optics instead of condensing it... and that we use heat-resistant audio drivers).

Thank you in advance,

Ennis

Please help🙏

I'm creating a fictional material called terrasium that should have

1- is like mercury, can melt in room temperature, but it needs electric catalyst, in this scenario it will be the brain electric waves. It can still melt without electricity but it would require extreme temperatures

2- in it's solid form, it can handle anything between a car crash and a speeding bullet

3- it can react to electricity, specially brain wave electricy. It's not like it dissolves or anything but it changes it's form

I have got 4 ideas in mind for it and I want to know which ones are physically/chemically possible

1- it's an undiscovered compound like oil that has all these properties

2- it's an undiscovered element that has all these properties

3- it's an undiscovered compound, that when processed and made into an alloy have these properties

4- it's an undiscovered element, that when processed and made into an alloy have these properties

👁️👁️🫖

basic engineering mechanics

asking for the first time in this sub

the thing is this question is so ... idk what ..

Say someone fell into a pool of a thing (liquid) from the 20th floor of a building

What are the properties of the said thing should have so the person doesn't turn into a human apple pie

I know there is no such a thing in real life, so theoretical physics time

So, I'm writing a novel and trying to make it as realistic as possible

But in one scene of it there is a character that jumps from 20+ stores building into a truck full of specific material and survives

So, obviously, no known material on earth can save you from that fall, not even none-neutonic materials, specially that the material is supposedly an undiscovered material/element that popped out of the ground as a result of WW3

So here is the three things I need this element to be able to do

1- able to withstand impact anywhere between a car crash and a speeding bullet

2- withstand extreme heat, I don't know how much yet but probably 1000 Celsius MAX

3- sure, the one thing I made this post for, someone can fall into a pool of it from 20+ stores high and not die, or at least some minor broken bones (this specific section as far as I know, excludes none-neutonic materials)

4- have some kind of reaction to electricity, specifically human brain wave

5- can transition between liquid and solid, for example if I wear a mask out of it permanently, with the right adjustments, the eye area of the mask can turn liquid and spread around the other parts of the mask which is still solid so I can do eye surgery for example

Can, all these properties, be physically and chemicaly in the same material?

In other words, would a physicist or a chemist crash out on me?

Hey everyone,
If you are diving deep into the Rigid Body Mechanics unit in IB Physics HL, or if you are currently brainstorming ideas for a top-tier Physics Internal Assessment (IA) or Extended Essay (EE), understanding rotating frames of reference is an absolute goldmine.
One of the most fascinating—and often misunderstood—topics in this realm is Coriolis acceleration. While it pushes into advanced mechanics, mastering it provides incredible depth to your understanding of rotational kinematics and can heavily differentiate your IA/EE analysis. Over on the Tesla eduventures channel, I have put together a comprehensive breakdown that builds this concept up from scratch, focusing on the visual kinematics of a block moving across a rotating disc.
Here is exactly what we cover in the breakdown:
Ground Frame vs. Rotating Frame: We start by establishing a clear understanding of centripetal and tangential acceleration from completely different observer perspectives.
The Vector Derivation: Walking step-by-step through how the changing direction of relative velocity generates the Coriolis acceleration component.
Total Net Acceleration: Compiling the Coriolis, relative, centripetal, and tangential accelerations into one complete, overarching equation.
The Ultimate Challenge Problem: We apply the derived concepts to tackle a famously rigorous, university-level physics problem. If you can follow the calculus and vector integration here, your HL mechanics foundation is completely rock solid!
Watch the full deep-dive here: https://youtu.be/0dnjYvux1NU?si=vmBbCMbyhBzZ1pbe
If you get stuck on any of the vector cross-products or integration steps, drop a comment below the video or right here on the thread. Let's master these advanced rotational concepts together!
— Vaibhav Agrawal

have a fun little real life project, trying to see how much force is produced from 1kg input, through a machine, to the output.

Problem is, I don't remember any sort of problem in high school or uni, and it's been a few decades since then anyways.

Specifically - I'm hoping to learn how to calculate force in = force out form a screw - is it the internal diameter? The external diameter? And Gears - sure a ratio is #in vs #out, but isn't it really the wheel and axle, and the # of 'teeth' doesn't matter? Or is it able to used as the same.

As shown, any Bill Nye / Beakman's World / Mr. Wizard or even Professor Julius Sumner Miller style, would be greatly appreciated

I've doodled up the system as is reduced into the simple machines between input and output, if I can learn what variables are required I'll re-make it with the labels:

Example:
- Lever = Mass Side A / Distance to Fulcrum = Force Side B / Distance from Fulcrum
- Wheel & Axle = Force Input Diameter (the grey line) = Force output diameter (blue circle
- Gear Reduction = Input Diameter (teeth count?) = Output Diameter (teeth count?)
- Wheel and Axle Force Input Diameter (purple Wheel) = Force Output (MINOR diameter - cyan rectangle)
- Screw = I have no clue...
- Increased Surface area = Force in / Surface area = Force Out.

I think that's everything required. Again, haven't been a physics student in a long while, and would love to learn/relearn how to do this! Yes, we're just at the 'label variable' portion, that and 'identify equations'.

SUPER bonus points if we can do a bit of 'friction' calculations AFTER the theoretical frictionless calculations.

Thanks!

During the motion of walking, does the entire body move in exactly the same way as the legs and arms?

Un semidisco di raggio R ha una densità superficiale di massa dipendente dall'angolo polare \theta, data da 𝜎(𝜃)=csin(𝜃) (con c da determinare in funzione della massa totale M). Il semidisco è incernierato nel suo centro di massa G a un perno fisso ideale su una parete verticale. Il diametro rettilineo del semidisco è collegato a un suo estremo a una molla orizzontale di costante elastica k, il cui altro estremo è fissato alla parete.
1. Calcolare il raggio di inerzia del semidisco rispetto al perno.
2. Trovare l'angolo di equilibrio stabile formato dal diametro del semidisco con la verticale.
3. Al sistema in quiete viene applicato un impulso orizzontale J sull'estremo inferiore del semidisco. Calcolare l'impulso minimo necessario per far ruotare il sistema fino a comprimere la molla della metà della sua lunghezza a riposo.
4. Trovare l'equazione delle reazioni vincolari impulsive orizzontali e verticali sviluppate dal perno in G.
5. Calcolare il periodo delle piccole oscillazioni attorno alla posizione di equilibrio.
V

If you’ve ever struggled to wrap your head around the exact difference between free oscillations, forced oscillations, and resonance, this quick 90-second Short breaks it down perfectly using a simple swing analogy.
It visually explains 3 scenarios:
Free Oscillation: Swinging naturally at a set frequency with no resistive forces.
Forced Oscillation: Applying an external force mid-swing, which alters the natural frequency.
Resonance: Waiting for the swing to reach its extreme point before pushing—keeping the natural frequency the same while continuously increasing the amplitude.
It’s a great visualizer if you are a visual learner. Check it out here:

https://youtube.com/shorts/IgOSkoxkJyM?si=EDD9QXHQpro3YctG

Hi everyone I am an incoming university student who needs to build a physics foundation completely from scratch I have never studied a single physics course in middle school or high school My starting knowledge is at absolute ground zero (Self-study) I want to bridge this gap before my university courses begin so I don't lag behind I am looking for structured self-study resources textbooks YouTube playlists or modular roadmaps that cover basic middle and high school level physics If you were starting from absolute zero what specific learning path or resources would you recommend to build this foundation fast and effectively Thank you so much

I’ve got the exam on Friday but I’ve got difficulties understanding the part of the dynamic and mechanics of rigid body and also thermodynamics. Can someone help me pls?