I have trouble understanding the subtlety between force and power.

Let's say I have a 1 kg weight. I want to lift it by 1 meter, it will take me 10 Joules of energy, if I lift it in 1 second, I need to apply an average power of 10 W. If I want to lift it in 0.2 second, I need an average power of 50 W. But to lift it faster I need to apply more force so in this case more force is equivalent to more power.

So in what cases you can apply more power without applying more force or apply more power without applying more force ?

Maybe my premise is wrong, in which case I appreciate being corrected, but IIRC if we compare two points in space with a gravity gradient between them, then the GR gravitational time dilation factor between these points turns out to be exactly the same as the SR velocity time dilation factor for the escape velocity needed to reach the point with lower gravitational potential from the higher one.

First, is that correct?

If so, I wonder if someone can offer any intuitive explanation for why this has to be the case. Of course I know "that's what the math shows us" but I feel that if this is indeed the same factor then somewhere in that math there's some unique perspective that shows us how velocity and gravity are related or somehow emerge from the same underlying mechanism.

I had this thought while thinking about circular polarization. My understanding of circular polarization is that it is achieved by superimposing perpendicularly polarized rays 90 degrees out of phase. The resultant light wave has a polarization that rotates once per cycle for whatever the frequency of the light is. It was taught to me like this.

If we superimpose 2 light rays of the same amplitude that have perpendicular polarization and these light rays are in phase, this will result in a light ray that has diagonal polarization and an amplitude equal to the square root of 2 times the amplitude of one of the component waves. This is straight forward vector addition.

If instead, both the polarization and phase have 90 degree separation, the vector sum of the amplitudes will rotate in time with the frequency of the light. If the two rays have 90 degree phase separation but one wave has a polarization that is not a multiple of 90 degrees rotated from the other wave, this creates elliptical polarization, the polarization is still rotating with the same frequency but now the magnitude oscillates in time as well.

180 degree polarization rotation of an "in phase" wave is kind of the same thing as light of the same polarization that is 180 degrees out of phase. I don't think I can try this with a polarizing filter. I suspect a simple polarizing filter can only effectively rotate polarization up to 90 degrees. Does a polarizing filter simply allow any light where the E wave component is aligned with the filter to pass?

This is a bit confounding. 180 degree out of phase light superimposed should deconstructively interfere. My question started with unpolarized light, but in asking I realized that the problem also may exist for light polarized by a filter.

Incoherent, unpolarized light should have more or less uniformly distributed phase and polarization. When all these waves add together how is it that we wind up observing any light at all? Is it that what we are actually observing is just a few randomly polarized waves that somehow punch through this noise? What happens to the energy of the waves that cancel out?

English is my not firstlanguage so beat with me. I had a physics test I aced but got B. I lost like points on whole question because I didnt convert mH, mA, ms into H,A, s. Whole thing was correct just final result was in mili values. I thought I didnt have to convert because all values if converted would have sdditional 10^-3. Professor told me its all incorrect and I just got lucky I got values correct but I only see logical fallacy in that. I know I cant calvulate ms and J but all values vere in milis and I am fristrated because it costed me my grade. I just wanna know if I actually made mistake or not

Let's say we have two sufficiently large, insulated, sealed containers. The only difference between them is that one is filled with air of normal temperature, pressure and density, and the other is a vacuum. We name the air one "chamberA" and the vacuum one "chamberB".

Take an ordinary bamboo dragonfly and measure the speed of its rotation when it can hover in the air. E1 is the rotational energy corresponding to this speed.

P.S. Bamboo dragonfly is a little copter. It is a toy that originated in East Asia and later spread to Europe. It is the ancestor of the helicopter.

Create a special bamboo dragonfly that has the same total mass as an ordinary bamboo dragonfly. What's special about it is that its blades and pole are not integrated but connected through a rough bearing. make the mass concentrate on the pole section so the two parts don't reach co-speed too early. We name the ordinary one "dragonflyA" and the special one "dragonflyB".

Use a separate motor to consume the electrical energy of E1 to drive dragonflyA to rotate, then release dragonflyA from a height H. All this happens inside chamberA.

Use the same kind of motor to consume the same amount of electrical energy of E1 to drive dragonflyB to rotate, then release dragonflyB from the same height H. All this happens inside chamberB.

Since the center of gravity of dragonflyB is slightly lower than that of A, in order to avoid the two turning over after landing and causing different energies transmitted to the floor, both fell vertically into a hole of the same depth. In this way, we ensure that the changes in gravitational potential energy of the two are the same.

When all macroscopic motion ceases, measure the total heat change in the two chambers separately. QA is for chamberA, QB is for chamberB. 

On stack exchange, people are divided into two groups. One group believes that according to Newtonian mechanics and James Joule's experimental results, QB = mgh + E1, and QA = (mg-F)h + E1, QA < QB. (The integral symbol should be used here but it is too difficult to type)

The other group believes that according to the law of conservation of energy, QA=QB，But they have no way to prove it mathematically.

Because this would require demonstrating:1，dragonflyA makes significantly more energy dissipate into air than internal energy generated by friction of dragonflyB when the rotational energy of both decreases by the same amount. 2，the extra energy at any given moment is equal to the ΔEp of draonflyA minus its current translational kinetic energy.

Who is correct? Both?

I am having a problem in this question:- A beam of electron and another beam of protons (both having energy 16.5eV) are incident separately on two identical barrier respectively each of 10.2eV high and 10˚A wide. Which of the following is correct a. electron will have greater transmission compare to protons b. protons will have greater transmission compare to electrons c. both have equal transmission d. neither proton or electron can cross the barrier I calculated transmission probability for both and the proton has 0.988 and electron has 0.980 probability of transmission. So the answer is coming option b but the answer should be option a as electron has more velocity and should have more transmission probability. I tried asking both Chatgpt and Gemini and they are agreeing on option a. But what's the catch?? The transmission probability formula should give higher value for electron.

Hi everyone, has anyone received acceptance mail from vssc? I opted for dec 20th to jan 16th slot and wanted to know if the announcement for this batch have started.

IN THE QUESTION(A horse was pushed with a force of 45.0N thereby doing 250J worth of work. calculate the distance that the horse was pushed) is it possible to find distance with only work and force.

When we do a renormalization group transformation we integrate out high momentum modes. What does this look like in position space?

High momentum = short distances, so does integrating out high momentum mean that we are integrating out some neighborhood of the origin in position space?

Hey everyone. I will soon have a gr12 (Canada) culminating assignment in physics that I hope I can take advantage of and boost my mark. The assignment is to create an "impulse reducer" to pass an egg drop challenge at heights of 1, 2.5, and 5 meters. Basically the rules in terms of the device itself is to fit within a 15cm x 15cm x 15cm cube and it has to be cool or unique. As in it cannot just be a box with packing styrofoam or anything along those lines. Easy access to the egg and just thoughtful design in general will get you marks. So will quality engineering, reusability, etc. Oh and it needs to be quite light - less than 90g (crazy to considering a phone is typically around 200g these days).

Any ideas or inspiration? Not necessarily full blown ideas but just anything to point in the right direction? Anything absolutely geeky I can add to it (that's reasonable in price) to make it stand out?

My current idea at least for the egg housing is something sort of like a box in a box with the inner egg compartment being suspending with like rubber bands in all directions and maybe the elasticity will help disperse the force all around the contraption?

EDIT: just to clarify this contraption will fall with the egg, ie it will go around the egg and protect it. its not a catching device.

Kind of a wierd title but here is a more detailed version of what I am asking: I own an SUV that has both front and rear wipers. I year round always have purchased the most concentrated and below zero capable windshield wiper fluid. Where I live that would be -35F capable fluid. It is getting cold where I live quickly and I am sick of the windshield wipers getting stuck after the car sitting outside at work for 12 hours. A friend told me a secret to avoid this is to spray for 10 seconds the windshield wiper fluid button on the front and back. The only let the windshield wipers wipe once or twice. The liberal amount of fluid that coats the windshield and the wiper part that actually touches the windshield will prevent ice from sticking the windshield wipers from getting frozen to the glass. I asked a physics geek friend of mine about this and they said do not do this because there is only a little anti-freeze in the fluid and it will actually make the problem worse.

Recently took dig a bit in to tensor calc/geometry and notice that relativity is mainly Riemannian geometry based (curvature tensor ect) which differs from the QFT that I learned before just wanting a clarification

The eldest niece is 13 years old, and a fan of studying all things physics. Last year some t-shirts with physics puns were a holiday gift hit. Alas, I’m stumped for additional ideas. I’d gratefully accept any suggestions you might have… a fav gift you’re received? Book recommendations? Quirky toys? Experience suggestions? Thanks!!

title

Escape velocity makes no sense to me. If two objects are moving apart, won't the relative speed always decrease, regardless of their relative speed? And if relative speed decreases, won't it eventually become negative meaning that escape has not happened?

Everybody is constantly telling me (and I agree) that time just seems to be flying by faster and faster, months dropping off the calendar so fast.. I remember when I was a kid the summer lasted so long, or a day felt so long, and I always chalked it up to you experience time quicker as you get older..

But somebody's post on YouTube revived the a memory from when I was little: I was taught (and maybe a lot of you were too) that you count off seconds by slowly and calmly saying "One Mississippi, Two Mississippi, Three Mississippi, Etc." and really back then that's how long a second on the clock would last.

If you try that now you get about 2 seconds gone by whilst saying "One Mississippi" in the cadence that we used to count it off.

I did a little experiment and it was really cool, and if you remember the Mississippi thing from when you are were younger you could try it too: I was heating up some food in the microwave and it just struck me to do this, but I looked away from the clock and basically stared at the ceiling, and decided 'normalize' my body clock by counting off "One Mississippi, Two Mississippi, Three Mississippi, all the way to Ten Mississippi". By ten, I had slowed myself down internally, like my I guess 'anxiety' level had went down, and I was feeling really calm and normal kind of like how I used to feel back when I was younger, in slower paced times, like my body clock had gone back to normal, and then I looked over at the clock on the microwave, and the seconds were just FLYING by, "28, 27, 26, 25, 24 ..." SO fast like double time fast or something.

I'm just wondering like, is it possible time has sped up somehow or what could the answer be, cause I certainly remember what a second was when I was a kid, and how long a day lasted, or a summer holiday, and everything is just so fast paced now.

Has anyone else noticed time going by faster than it used to? Like is it possible time is 'actually' going by at a different rate than it used to? Do these things change? Is there a possible like, scientific reason that could support this (different positions in space, or proximity to objects in space) I know time doesn't actually go at the same rate all throughout the universe, like in Interstellar. Could it have change over the last few decades?

Anyways just thought I'd throw that story out there and see if anyone else notices this as well.

Hello! I'm new here and I'm terrible at physics, and I was wondering if you guys wouldn't mind helping me with a problem for a personal statement I'm writing for Medical School. I know I posted this a few days ago but I only got one response and the helpful soul who tried to assist me has vanished.

When I was 17, I was in a theatre accident where a 4x4 standing straight up slipped and fell, hitting me in the back of my head (about the back right parietal lobe). I'm trying to figure out how to calculate the impact force of the post for the writing.

A bit of information:

- 4x4 was about 12 feet tall (making it about 25.4kg) and suspended in a bucket on wheels about 8 inches off the ground

- I am 5'5" tall, but I was somewhat crouched so standing at about 5 feet at the time of impact

- I was pushing the bucket forward to set the scene but the upper part of the set broke, causing this 4x4 to fall and hit me. When it started to wobble, the wheelie part shot away, knocking over the bucket and allowing the 4x4 to come down and hit me (who was in the process of standing to full height) in the head.

- 4x4 probably hit me at about 9 feet up the side of the 4x4, so 3 feet from the top

- 4x4 physically bounced off my head, kinda compressing my neck a bit (I felt it)

- It was more of a glancing than direct impact (kinda clipped me) and it happened in maybe a single second.

I took introductory physics in college but this is WAY beyond my capabilities so I was hoping you could help me? I don't need it to be perfect, I just need it to be approximate so I can see how close I was to cracking my skull. I need a good hook for my personal statement, if you guys could just please show me how to set the problem up, I could try it myself, I just don't know where to start and you guys are the experts.

So in relativity, length/distance depends on your frame of motion. How does this relate to particle interactions in QM taking place over short distances? If the distance isn't the same in all frames, how do particles "know" when to interact?

I recently came across this reddit comment

The free theory of gravitons, in which you can rigorously define graviton states, is of course linearized, by definition. However if you turn back on interactions and limit yourself to tree-level (since you don't want quantum corrections) you can actually rederive the full set of non-linear field equations.

This is completely analogous to how you can obtain classical electrodynamics from a theory of photons at tree-level.

My understanding is that tree-level diagrams correspond to a classical theory, but is it possible for one to derive the full set of relevant EoMs?

The closest I've seen for EM is deriving the electric potential for two point charges, from the tree-level diagram of two charged particles exchanging a virtual photon. But anything else more than that I'm unsure of.

So I’m a senior undergrad physics international student in US graduating with BS next sem. with one research in biophysics which I didn’t enjoy a lot, I am looking to apply for grad schools today and I am so lost because I do not feel like doing phd anymore cause as much as I love particle physics and would do research and be a professor, the paycheck doesn’t seem worthy of time put to get PhD. I want a field where I have time to make a million a year after 10-12 years of work or do my side startups which I do not feel is possible for my case where I’m doing undergrad from simple good university, not Ivy League so being professor won’t make me rich. Doing PhD and then teaching for 20 years to make 150-200k doesn’t seem worthy as this is more easily achievable I believe in industry with comparatively less work than PhD physicist. I thought of industry and ChatGPT recommended masters in engineering physics or applied physics but what if I don’t get in, as an international student in US; I haven’t done any internship and got 0 experience for industry to know if I’ll like that more than academia or research or less. PlusI genuinely wanna be rich…and willing to work hard but in a field where I’m paid worth my time and effort…not just given praise for say, paper publications, I’m so lost and in pressure of time…can you help me ?

Hello! I'm an IB student from Singapore and I was wondering if anyone had some good recommendations to buy a decent digital aerometer to measure air density online. I've tried looking, but most of the listings I get are for anemometers or they are of aerometers, but the pages are missing.

I need to measure the air density of the surrounding air for my experiment on finding the drag coefficient of a specific ping pong ball.

I have read that I can calculate the air density as well, so if I cannot find an aerometer, would you recommend I buy an anemometer and do the caluclations myself? If so are there any good recommendations for that as well?

Thanks so much!!

Sonic booms happen when something goes faster than sound and light is faster than sound. What gives ?

As in, what is the space of all possible postulates? How would you even begin to think about that? Would you have to start at quantum fields and move up from there?

Hi! As u can tell by the title, I’m having a bit of trouble on my physics homework.

This is the problem:

Context —> Force Q is <4,-2> & Force P is <-3,-3>.

1. find Q + P = R
2. find the magnitude and direction of R
3. sketch P + Q using tail-to-tip drawing and see if it works.

I tried solving it and I finished the first part. I got <1,-5>. However, I don’t rlly know where to start on the second and third parts of the problem. If you can help, it would be very much appreciated!

Thank you for your time!!

If you refract light, however many times, then refocus it, did you lose energy? If so, what happened to the photons?

A couple of weeks ago, I watched The Plasma Channel's video: Creating an Exotic Material With A Static Secret (Electret), on YouTube, and just now wondered: Could a similar kind of particle manipulation with gluons affect the Strong Nuclear Force in a similar way? Now as I type this, what about manipulating W and Z bosons to affect the Weak Nuclear Force ("Weaket"?)

Is there some inherent looping quality to infinity?

I had physics in school a very long time ago, so I thought I would know the answer to this question, but I dont - so Im coming here for help. Intiuively the two scenarios im presenting, should not be different, but Im not 100% certain.

Assume

1. Car A is travelling at a steady 30 km/h and hits a pedestrian.
2. Car B is travelling at 10 km/h but hits the throttle to go to max speed. As car B is accelerating it hits a pedestrian at the exact moment it reaches 30 km/h.

In both cases the cars come to a full stop after hitting the pedestrian.

My question is: Does car A and B hit the pedestrian with the same force? Why/why not?

Ps: The question came up as my wife chewed me a new one after accelerating too quickly (I get that reaction time and awareness probably goes down when you are accelerating)

Edit: The "moving" word in the title should be removed, but I cant seem to edit the title.