Physics Definition and 985 Threads

I was thinking about an idea of a calendar epoch based on the field of physics, and its thinking about which event should be used as the epoch so I have this idea and just wondering what you guys might think about it I initially landed upon two ideas, one pretty ancient and the other kinda...

I have made solutions a-d, but my fermi velocity seems too big.

At what point during study for a reputable physics degree should one normally encounter the "Jansky"? I.e., at what point is it reasonable for a lecturer (or textbook writer!) to assume the existence and meaning of "Jansky" as basic prior knowledge?

I first thought that the angle would have to be maximum when it is closest to the critical angle for total internal reflection. From my lectures the equation for the critical angle is ##\theta _1>\ sin ^{-1} \left( \frac {n_2} {n_1} \right),## so as ##n_2 = 1##, we have ##\theta _1=\sin...

In physics pedagogy, the routine is to introduce new material in lectures and then practice the material in end-of-chapter problems. This problem, shown below, familiar to many of us on PF, is my favorite. One must get to intermediate mechanics class in undergraduate physics studies to finally...

Hello. I am a non-traditional undergrad, currently conducting materials and electrochemistry research (optics, photonics, semiconductors, energy storage). Before going to college (post-secondary), I had extensive experience in bioinformatics and biomolecular research. Although it is not yet the...

Hello ! I have a problem understanding how light works in multimode optical fiber. What do I mean in single-mode optical fiber there is single light which contains information. In multimode there can be multiple lights with multiple information. Like here 1st picture contains multiple...

I'm a retired Engineer. I want to learn methods to formulate equations to ask questions of physics phenomenon. What school teaches this and by whom? Can anyone point me there?

Alain Aspect got a Noble Physics prize for experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science. According to this article https://phys.org/news/2022-10-quantum-entanglement-spooky-science-physics.html Aspect is quoted as...

Quantum entanglement...

https://www.nobelprize.org/prizes/physics/2022/popular-information/ Using groundbreaking experiments, Alain Aspect, John Clauser and Anton Zeilinger have demonstrated the potential to investigate and control particles that are in entangled states. What happens to one particle in an entangled...

My child is learning the periodic table for science class, memorizing elements 1 - 20. Middle school. While I assisted, I mused on the elements and on which are discussed most in physics classes. Here is my ranking of the top three: 1. Z=1 2. Z=2 3. Z=92 Do you agree?

Interesting... "Physics Nobel nominees, 1901–70" https://physicstoday.scitation.org/do/10.1063/PT.6.4.20220929a/full/ is an update extended to 1970 of "Physics Nobel nominees, 1901–66" (2017) https://physicstoday.scitation.org/do/10.1063/PT.6.4.20170925a/full/ related...

Hi, I'm trying to calculate my own physics problem but didn't get it something. When I'm trying to calculate the impulse of the object when it's hit by F=10N force in the smallest possible time, then should I write: dP/dt = Fnet => dP = Fnet*dt ? Another question: In general, if I calculate...

Hello I am a physiology student who is curious about the physics underyling blood flow and pressure. I have taken physics classes however at the elementary level the focus is on ideal fluids in systems with no friction. I would appreciate any answers or if you could point me in the right...

what is the reason for that the energy hypersurfaces in a phase space, which belong to systems with constant energy are closed? ( see picture )

Summary: Predictions for the 2022 Physics Nobel Prize As the Nobel week is coming closer, what are your predictions for this year Nobel Prize in physics?

Hello, I am trying to figure the strength (in lbs) of a strap needed to attach 2 Rolls together without breaking. Each wheel has a weight of 1000lbs and a diameter of 30in. If there is required information missing, let me know.

Hi all! It's been a decade since I graduated with a bachelor's in philosophy. I went to an ivy planning double major with physics, but I ultimately dropped the latter after my introductory courses and graduated with a poor GPA (2.7). To save you the sob story, I basically had no ability to cope...

Homework Statement:: nuclear/atomic physics research problem Relevant Equations:: research problem please Hi all Anyone who can help me to get a research problems based on advanced nuclear physics please... Thank you all

I am currently a final-year undergraduate student whose primary major is Physics. I double major in Computer Science, and my grade is currently near-top in my department from a prestigious university (non-US, top in my country). My research experience during undergrad has primarily been about...

Ok, so here is what i am trying to do. Find apogee of a model rocket i built using a C motor, then i need to calculate terminal velocity, but something is not adding up, i get a really really high apogee, almost a mile. STAGE 1: I have a c6-7 rocket motor which provides 10N-s of impulse, and...

I am looking for good textbooks in physics, algebra, and trigonometry textbooks that are up to date and a good read. I heard that Feynman’s Lectures was really good. Is it still up to date enough? Any opinions?

I was modeling the dynamics of a vehicle for a project, and started doubting about the way of applying physics in this particular case. The thing is, I know the torque in the wheels from the torque the electric motor I designed do provide, multiplied by the gearbox ratio. I also know the...

Summary: doesn't this decrease entropy ? Cellulose is known for its hydrophilic quality, which can be explained from the polarity of its hydroxyl groups. We all know water can overcome the force of gravity through a piece of paper you put in the water. Correct me if I'm wrong but this is a...

Hi, this is my first time using the Physics Forums so please let me know if this question belongs somewhere else. I'm a senior undergraduate at a mid-size institution in the United States seeking to purse a PhD in High Energy Theoretical physics or Quantum Information/Computing. I'm aware these...

(I need help with the 2nd part as I can answer the theory part properly). For E=4 eV we can find the wavelength of emitted photon. E= 4 eV = 6.4087e-19 J Using E= hc/λ we get λ=310 nm (approx) My doubt is that this should fall in the Balmer Series but we know that the lowest wavelength value...

This is a homework problem of my grand daughter. The question is to find out the conditions of an object M on a slope with angle shown and applied force "F". I find there are 3 conditions, sliding up, sliding down and not moving. This is my work. I just want to get comments on my work: At the...

Where the fingers (extended) go first, then only the knuckles. Is it supposed to be more effective? I believe it will break your fingers instead. An example

The editors of high impact journal Nature Physics explain why the field of quantum foundations is important for physics. https://www.nature.com/articles/s41567-022-01766-x

I'm a researcher hoping to look at some papers on the technical aspect of water physics on a water slide. Does anyone have resources or pointers for me? Essentially, I'm trying to find the optimal amount of water needed to propel a passenger down a standard straight water slide, but I don't know...

My girlfriend is in her undergraduate biology course, and one of her professors said the following sentence: "Physicists are jealous of Biologists, as their field has been stagnant for years, with no new things to discover." I know this isn't true. I even got to argue with her about how this is...

Hello. I wonder about the most important secrets of physics today. Once it was the "secrets of atom". Countries were in a race to be the first to do "atomic bomb." For that reason, America started the Manhattan Project. Similary, do you know names of the most important developments of physics...

As I was looking for an example for a metric tensor that isn't among the usual suspects, I observed that the Cartan matrix I wanted to use is positive definite (I assume all are), but not symmetric. Are the symmetry breaks in quantum physics related to this fact?

Hello, I am currently preparing to learn the 8.01 course "Physics I" via the MIT OCW and I am trying to find an adequate textbook for that purpose. In the three courses that I have found, the first two use: Young, H. D., and R. A. Freedman. University Physics. which is quite expensive in my...

Hi everyone, I'm new here but I've come across PF many times as viewer while searching for clarifications and exercise solutions. I think this should be the right place to ask for advice. My background: 30-ish years old, got my BSc and MS in Electrical Engineering in 2017. The courses were...

The measurement for astigmatism is diopter. But what does 1 diopter of astigmatism mean? Thanks a lot if you help me figure this out!

Is there any specialize articles that talk about how Astronomy can help learning Math and Physics? In particular, how observational astronomy can help in the learning process of Math and Physics.

Hi guys! I'm a master's student majoring in nuclear engineering in graduate school. I have a few questions while doing research, so I'm writing this here. My research is simple. We conduct neutron analysis to convert a research reactor using highly enriched uranium into a low enriched uranium...

How hard is it compared to undergraduate thermodynamics? Is it harder or easier?

If you enjoy both physics/science and history like me, you may enjoy this video from the Royal Institution. It's about groundbreaking experiments (no theoretical physics); X-rays, particles etc. I'm only 45 minutes in so I haven't seen the entire video yet, but I wanted to share it...

I recently graduated last year with a BS in Physics. To say that it was rough would be an understatement. I started off my degree very well, getting nearly all A's and A-'s. My performance would decline for various reasons, though mostly due to mental health which spiraled and became a bad...

Hello, I'm trying to learn calculus, what books would you recommend? For a beginner.

Can I get an online bachelor in physics because I live in a country with law education rank in natural sciences

I live on a lake, and have for almost 3 decades now. Every year I watch shoreline changes, from year to year and shorter timespans, sometimes just days. The lake is large in surface area at 236 km2 (91 sq mi), but with an average depth of only 28' probably relatively small in volume for its...

I am going into my senior year of hs next year and I am meditating on what I should major in. I have a keen interest in physics but also a love of math. The field in physics I would like to major in is theoretical physics/astrophysics, and the pure maths I am interested in are diff, algebraic...

Hi Pfs, When Stephen Hawking proposed the idea of black hole information it appeared that information could be lost. it was a problem in GR which is a dererminitic theory. Knowing initial data and Hamiltonian tells you what was and will be. It is not the case in quantum physics. things evolve...

I have been experimenting with a minimal "toy" physics engine for JavaScript, called verlet.js but now I want to switch to a more versatile and feature rich engine. One feature I would like to use is the ability to assign a reference angle to a pair of segments (i.e. links, i.e. distance...

Hi everyone, After completing high school, I will enroll this fall at a 3 year technical school in China studying industrial robotics, but I still plan on getting into an undergrad physics program at a later time. (Some colleges can allow a transfer to their undergrad program after technical...