Currently in quantum mechanics. A pure state is a vector, but a mixed state can only be described by a matrix. Why? My lecturer can't really explain it in any further detail than ”the state is unknown”. But then you should be able to write it as pure states with probabilities? Can someone give a thorough explanation as to why mixed states can't be expressed with pure states?

Force is going to be applied by pulling this chain until the metal lip of this SUV bends, which is made of steel. The lip is about 1.5 inches thick at its base. Force is going to be pulled in the direction of the anchor connector, but perhaps a bit shallower such as a 15 degree angel.

The question is:

Will the lip bend uniformly outward or will the lip bend as a curve with a sharp angel when pulling outward or is it even possible the anchor will leave a large indentation on the metal instead of bending evenly at all?

Any input is appreciated, thanks!

This is my slayer exciter tesla coil . According to Faraday's law of induction: the larger the magnetic flux, the larger the current. I assume my magnetic flux looks something like in the drawn image.

This should mean that when I position the LED coil parallel to the ground, it should light up the brightest and when it is positioned perpendicular to the ground, it shouldn't light up or with very low brightness.

But the video completely contradict this assumption. Can someone explain this please? Are there any flaws to my reasoning?

Here's the video I recorded: https://streamable.com/r54l6s

Thanks

Edit: Thanks for the awesome answers guys, I will read them after I am done with school

Also, I am very new to electromagnetism so my knowledge is very limited so please excuse me for the replies if I happen to understand your explanations

Maybe not the right subreddit, but I figured there might be some brainy people here who could give me some recommendations! :)

My boyfriend is turning 19 soon, and he's really interested in the technical side of physics, especially when it comes to cars, trains, and mechanics in general. He already owns a few books on these topics.

Do you know of any books that are technically challenging without being too dense or boring?

For context, we're both in our final year of high school on a science-focused track, and my boyfriend is particularly talented in these subjects. So, something that goes a bit beyond the basics would be great, but I'm not looking for hardcore university-level textbooks or anything too academic.

Thanks in advance!

I am doing a project for school and I really would like to interview a physicist in the industry. There are plenty already that work in education but I don't want to go that path so I would like to hear from someone in the R&D field how it's like working for a company or a country.

If anyone of you for this please respond and I'll send you my school email so that we can set up a teams call or zoom.

Thank You!

There are a lot of of physics research questions, perhaps some overhyped. Which physics topics/questions would one consider to have the most significant importance/applications in the next say 10-20 years?

Basically the title - I recently started my MS in Electrical Engineering and am thinking of doing a PhD in Applied Physics. Some of the schools i want to apply to for PhD require the PGRE. I have taken courses in EM and Quantum Mechanics, but nothing related to classical mechanics, stat mech, or thermo. How do I go about it? Any advice to fill in major gaps would be greatly appreciated.

Hi guys, I’m 24 years old, and I’ve completed my Master’s degree in Physics. But if you ask me whether I actually learned much during those years, my honest answer would be no. I failed to develop the knowledge, analytical thinking, and problem-solving skills that I should have gained.

I was distracted, misdirected, and wasted so much of my precious time watching porn, scrolling through Instagram and YouTube Shorts, and getting lost in daydreams. Before I realized it, the days had passed, and I had lost valuable years that I could have spent learning and improving myself.

Now, I’ve landed a job that is somewhat related to physics, but I’m struggling to perform well because of my knowledge gaps and lack of problem-solving skills. I know I need to change. I need to rebuild myself, regain my confidence, and develop the skills I should have developed years ago. But realizing how much I’ve missed makes me feel depressed and left behind.

I genuinely want to rewire my brain and recover my ability to think deeply, reason logically, and solve problems independently. However, I don’t know where to begin. Should I start from scratch with basic mathematics, revisit 10th- and 12th-grade physics, and then gradually work my way through B.Sc. and M.Sc. Physics? Or is there a better, more effective way to rebuild my knowledge and analytical skills?

One of my biggest struggles is that I can understand a solution when I see it, but I struggle to solve the same problem independently. I understand the concepts and can follow the steps once they’re explained, but when I have to figure things out on my own, my mind goes blank. I also feel an overwhelming urge to solve problems quickly. When I try to slow down and think deeply, I sometimes experience a headache and struggle to concentrate.

I don’t want to keep repeating the same mistakes. I want to break this cycle, rebuild my fundamentals, improve my concentration, and become someone who can genuinely understand physics and solve problems independently.

For those who have experienced something similar or have expertise in learning and cognitive recovery, please guide me. Where should I start? How can I systematically rebuild my mathematical foundations, analytical thinking, and problem-solving abilities without wasting more time? Is starting from the very basics the right approach, or should I follow a different strategy?

I know I cannot recover the time I’ve lost, but I want to make the best possible use of the time I have left. I’m ready to put in the effort. I just need to know where to begin and how to move forward.

I'm a y3 physics undergrad and I can't help but feel increasingly scared about my future and possible career prospects given the rapid advancement and involvement of frontier AI models (like Opus 5.5, Astra 6, and other internal models) in math and physics research - the pipelines of which grow increasingly more autonomous. I can't fathom what this means for physics (particularly theoretical physics) academia in general. How are aspiring physicists meant to be able to a) pursue the physics they want and b) get paid for it? It seems like the threshold for a foot into academia (especially for PhDs and postdocs) will continue to increase. Funding worsening everywhere doesn't help either. It seems hard to not feel despair given the likely future, and a rapid decline in funding and PhD and postdoc vacancies feel inevitable. What does this mean for aspiring physicists? Are traditional processes and roles in academia likely to be completely revamped?

To clarify, I'm referring to academia and the reducing need for human involvement in physics. Not the discipline itself (the growth of which is insanely exciting to experience). For as long as physics exists I believe there will always be new problems to work on. I'm just worried about the barriers to entry.

Hello everyone,

So I am looking to self study physics, and i have a few questions.

To preface, I'm not looking to become a physicist or an engineer or anything (i have nothing but love and respect for you guys) but rather looking to apply the calculus I know. I'm currently self-studying calculus and I'm currently on Calc. 3. I'm just looking to get a basic handle on everyday physics. I only have an interest in classical physics, don't much care about modern physics, mainly quantum stuff. So I guess my questions are:

1. Is it possible to sucessfully self study physics?

2. I'm torn between Physics by serway/jewett 7th ed. and University Physics young and freedman 13th Ed.

3. Do you have any tips on how to sucessfully study physics? Are there any lecture videos?

because for calculus, I watch Professor Leonard, then read the section and it's worked pretty well so far. I'm using Howard Antons Calculus 10th ed. and his books lines up almost perfectly with Professor Leonards course, so I'm hoping to have the same thing for physics, but that might be wishful thinking.

Thank you for taking the time to read this post!

https://doi.org/10.1088/1361-6552/ae3f71

I'm in undergrad currently, but it seems like everyone asks, when I bring up possibilities of research or career, what area do I want to go into? The issue is, they all seem interesting, none immediately stand out to me. How did you successfully find out what area it is you want to specialize in?

I’m a junior student and it’s my first time to participate in the science fair so any ideas?
I want it to be related to physics

I have started college and my first physics course is mechanics (calculus based) I am bad at relative velocities and observer frames and my syllabus is till work and energy, I am way too cooked it feels like I am not understanding a single thing, I have a mid term exam in 5 days, there are tons of problems and it just overwhelms, how to cope up with it. Please help me

Hello all, I am currently taking calc 1 and falling in love with math. I plan to major in physics/engineering but have not taken a physics class yet, though I am very interested in the subject from youtube. What are some good starter books I could read now before taking my first physics class to help get some foundational knowledge on the subject.

I’m going to take the PGRE in 12 days! Sad that I forgot many UG physics stuff. Any suggestions for this short time practice? I’m just using Claude and ChatGPT to generate quiz and practice them alongside with the Ohio State University’s open materials. But currently the situation is not good and I feel very nervous. Any suggestions you can give to me? Thanks in Advance!

Hey everyone!

I've been wondering whether the recessed numbers on a standard die could affect its centre of mass and, potentially, the probability of rolling each number. After all, the 1 has one pip, while the 6 has six, meaning different amounts of material are removed from opposite faces. Could this create a small bias? I'd love to find out!

I've started exploring a different design (see the 3D model). Instead of having a different number of holes on each face, every face has the same recessed circular pattern, divided into 12 equal sectors. This keeps the geometry consistent and symmetrical along the X and Y axes.

The numbers are represented by colouring the sectors black: 2 for the 1, 4 for the 2, 6 for the 3, and so on. The idea is to use the same material and density throughout, with the recessed design helping protect the colour from wear.

I'm keeping the conventional arrangement of opposite faces: 1-6, 2-5 and 3-4.

I'm still exploring the idea, so I'd love some feedback!

Could differences in mass distribution actually affect a die's probabilities?

Would this design help reduce potential bias, or am I overlooking something?

What software would you recommend for calculating the centre of mass and moments of inertia?

Would anyone be interested in helping simulate or experimentally test the design?

I'm not claiming this will make a perfectly fair die, but I'd love to investigate the physics and see what the data tells us!

Thanks for reading, and I'd love to hear your thoughts!

I have searched online on amazon and Flipkart but I cannot find any. Does anybody have it or someone ready to sell? Or any website can you suggest from where i can buy this book?

I'm currently doing a master's degree and trying to figure out what I want to do after graduation. My long-term goal is to work in industry, preferably in a job that still involves experimental work. My bachelor's thesis was in quantum optics, and my master's thesis will be related to nanolithography. I've picked some EE courses as well. Ideally, I'd prefer not to have to deal with clients that much or be on call (the latter is pretty much a dealbreaker for me). Night shifts would actually be a plus, though that's not a must. My programming skills and chemistry knowledge are nothing to speak of, but I am optimistic that these will improve with time.

Would you recommend pursuing a PhD? For those of you with a similar background, what do you actually do day to day? How did you end up in your current role, and would you recommend it?

Hi everyone,

I am a PhD student doing both experiments and computational physics ( mostly fluid dynamicswith Boltzmann equations) and leaning towards more computational day by day.

Currently I am using Julia, I find it pretty fast and easy to use.

Do you think switching to C or C++ will be a benefit? I am asking from a research, but also emplyment in industry point of view.

I discussed with many people, mostly from the DFT area, and most of them told me that Julia slowly will take up the lead for HPC code.

What.s your opinion on this?