Idea Definition and 811 Threads

I am studying basic mechanics and have reached the chapter on potential energy. However I am a bit confused about the difference between potential energy and the formula for the potential energy due to work done by a conservative force. I am not sure which of the following interpretations is...

Hello, Just like the title suggests, I am looking for DIY project ideas, that involves Thermodynamics, Robotics, and Artificial Intelligent. I would like to use C++ and Simulink. And I am able to purchase components, e.g. Raspberry Pi and electrical components. If you have any ideas for a...

I remember that the definition of temperature is the average kinetic energy. Then how about if I keep shaking a box, wouldn't the kinetic energy of the box increase and thus the temperature of it increase? (neglecting the thermal energy gain from friction) Also, is it possible to use...

This article about an "Armageddon" scenario says that astronomers don't have a very good idea about the density of asteroids. https://slate.com/technology/2019/05/international-planetary-defense-conference-asteroid-impact.html I had thought that they had a much better idea about it. Can't the...

I came across a reputedly true bit of Cold War spy stuff in a book "Farewell: the greatest spy story of the twentieth century" by Sergei Kostin. It's about a KGB defector, Colonel Vladmir Vetrov who blew the structure of the KGB to the French. As a result, the US sowed the seeds of a spoof...

I'm freshly fininished my 2nd semester of a first year physics undergrad program (A on every class excepts for chemistry because of some health issues that day) And these are courses that I'm taking for my first semester of 2nd year. ***Gened Political Science 3 credits Intro Bio Lecture 3...

I am interested, from a lay man's perspective mainly, in the incompleteness theorem but not sure I understand even on a general level what is being said. From what I recall, it states something like the following: in all formal mathematical systems there are certain statements that can't be...

Hi, I’m an upcoming physics major who currently plans to end up in graduate school. I’ll be attending a school with a good-but-not-great physics program and I was wondering: would double majoring in physics plus something else (like mathematics or computer science) make me a more competitive...

This study from Johns Hopkins University shows that even if we manage to nuke an asteroid and "destroy" it, it will have a core back, in almost 2 hours. Nuking them was a bad idea before, but now seems worse. More details here...

Exokat [catsuit exoskeleton] and Simbot 8.4 {invention idea} I was watching a documentary wherein a lady Quadriplegic was operating a robotic arm direct from her brain, and I thought to myself, what she needs is a catsuit exoskeleton. So I set out to invent one, don’t know why ~ I just like...

I've been a semi-pro photographer for a long, long time. I know the value of having a polarizing filter in my camera bag. I also wear polarized sunglasses for driving during the day. You can't beat 'em. I know some people who are complaining about these LED head lights from oncoming cars...

Hello everyone, I wanted to ask one question. My friend has a physics exam at school were the topic is to come up with a interesting yet simple physical device that would prove a single or multiple physics concepts. Now we were thinking that it would be interesting to experiment with the...

For starters, I'm 20 years old and live in the USA. I dropped out of school to work in the family business in a very small town of roughly 300 people, I have had no formal education since the first half of 8th grade when I was about 13. I would call myself a high school dropout, but it's more...

The velocity of an object is given by the following function defined on a specific interval. Approximate the displacement of the object on the interval by subdiving the interval into the indicated number of subintervals. Use the left endpoint of each subinterval to compute the height of the...

I am reading Paul E. Bland's book, "Rings and Their Modules". I am focused on Section 4.3: Modules Over Principal Ideal Domains ... and I need some help to fully understand the proof of Lemma 4.3.10 ... ... Lemma 4.3.10 and its proof read as...

Drive two 15m long optical fibers extended in opposite directions with a 1GHz pulse generator. The recievers at the end of each fiber are now syncronised sources of 1GHz pulses. Connect them to pulse counters, one of which provides a signal whenever a pulse train is present. Connect this...

I had a bit of a thought experiment the other day, does relativity mean that technically you couldn’t travel faster than the speed of light to the observer. But if you were traveling from Earth to another planet, could you technically be traveling faster than the speed of light relative to the...

I've been trying out a couple new running routes around work lately, and my run today through Levi's Stadium parking lot (yes, my work is right next to Levi's Stadium, oh joy) took me past light poles that have some kind of sensors attached to them. I wasn't able to figure out what they might...

First, not related to this figure, if there is a total torque T acting on a body, can I move this vector around the space by translation? Will I affect the system?Second, I don’t understand why can’t there be torque along the A-B axis. For example, if I apply a force to flip the gyroscope, the...

Any idea why mass slows time down? More mass more time dialation

I am a physics freshman in Europe where we have 3 year undergrad programmes. I am just over the first year of Multiple Sclerosis and just when the school started in october last year, things went very very bad. I was super ready for UNI and I started off very well with awesome routines, but I...

EDIT -- "Who wants it" -- Obviously with no obligation to me, since I'm publishing it on a public forum. :smile: So I just saw the very cute "Human Kindness" commercial on TV again, where the Dad sees his son with respiratory issues having trouble blowing out the candle on his 1 y/o birthday...

I'm studying QFT by David Tong's lecture notes. When he discusses causility with real scalar fields, he defines the propagator as (p.38) $$D(x-y)=\left\langle0\right| \phi(x)\phi(y)\left|0\right\rangle=\int\frac{d^3p}{(2\pi)^3}\frac{1}{2E_{\vec{p}}}e^{-ip\cdot(x-y)},$$ then he shows that the...

Recently a Chinese article was published that claims a new LIDAR technique for atmospheric sensing. The article only consists of the Abstract with no further information. It is very brief which makes me suspect this is someones pipe dream. A link to the article is given below. The "new" concept...

I am beginning my senior research project and I am unsure of what to have for a topic. It is an English class but I plan on doing it on either STEM or history. Any ideas

Hi, I was thinking about smps power supplies and for the record I have built a few myself, so normally in a more powerful smps you want to implement a PFC stage for both "grid health" and efficiency, although I assume usual linear supplies with a mains transformer and a bridge rectifier with...

I have been trying to understand the role of a cavity as a black body radiator in the derivation of planks black body radiation law but it has left me with 5 main questions: 1. If an object is a perfect absorber it must also be a perfect emitter, meaning that (allowing for a cavity not being a...

Greg Bernhardt submitted a new PF Insights post A First Idea of Quantum Field Theory - 20 Part Series Continue reading the Original PF Insights Post.

Dear Everybody There is a ball which has mass of 11 grams is thrown straight up with an initial speed of 4 m/s. Assume the air drag is negligible. a. What is the kinetic energy of the ball (in J) as it leaves the hand? b. How much work is done by the gravitational force during the ball's rise...

Elon Musk says we can terraform Mars by converting its CO2 and H2O into CH4 and O2 using solar power, the latter two compounds being quite useful. Can't we use his idea to reduce the CO2 in our atmosphere and reverse global warming?

In this example: The input multiplier to the artificial neural network, at the bottom of the screen, for each note is determined by an output of an Expectation Maxamazation sequence that converges after ten iterations with input of the artificial neural network's output above a threshhold...

This is an experiment/project idea inspired by Jules Verne's "The Mysterious Island" and also the "Biosphere" experiments. I thought it'd be a cool discussion prompt. In the book, a bunch of men are shipwrecked (well, baloon-wrecked) on an Island. One thing I love about the book, unrealistic...

Hi. First, let me introduce myself: I m from Brazil, I studied physics a few years ago and I ended up leaving the course, today I work with software development. I would like to know if you can help me to take a doubt: I came up with an idea that an electron could move so fast that it would...

I think the story where abelian, i.e. U(1), gauge symmetry comes from is pretty straight-forward: We describe massless spin 1 particles, which have only two physical degrees of freedom, with a spin 1 field, which is represented by a four-vector. This four-vector has 4 entries and therefore too...

Could this FTL idea with a fast moving large mass be possible? I have recently come up with a possible way to achieve faster-than-light (FTL) travel by using a high speed singularity or large mass. Background As everyone knows, according to relativity, under normal conditions, it is impossible...

One of the conditions to distinguish Simple Harmonic Motion from other harmonic motions is by the relation that a∝x where x is the displacement from the point that acceleration is directed towards But what confuses me is the constant of proportionality introduced to this relation: ω2 ω is...

Hello, is this stupid? is this project possible, about 1,500 usd. I know the key is evenly distributed flow, so maybe two small motors. Maybe add a grate? this vid gave me this idea: thanks in advanced if anyone reads this thread

Hiya! In school we have tha task to create our own phy lab. I am going to investigate the width of a hair using wave diffraction (a laser maybe?). Does anyone have any creative ideas on how to develop the lab to make it more uniqe and interesting. E.g measuring from different distances. Or...

When we learn about energy and momentum at high school it can be taught by simple equations in a 1 hour lesson. So why did it take over 100 years from approx 1690 to 1790 for energy being direclty proportional to v squared to be accepted by the wider scientific community. Also shouldn't the...

My creationist grandpa says that we are at the center of the universe and that other galaxies are in spherical shells around us and claim that this means we are in a special place in the universe. Basically he believes in the "quantized redshifts" thing you may or may not have heard of, which...

Most students struggle with probability because questions usually involve FUZZY word problems. I am reviewing precalculus right now. In the later chapters of precalculus, a touch of probability is introduced. Can someone explain the basics of probability? I know, for example, that all...

Hello, I'm doing this year (and the next one) a paper for Physics. I know you guys think is no big deal, because I'm in high school and so. But currently the level of my school is really high and most of the people are doing real research papers. The thing is I have no idea what to be the...

Hello, Physics forum community.I have a project for an intro to engineering class in which I must design a system to solve an environmental problem. This class is only an introduction so I'm not sure how detailed and specific our work has to be. I must have been feeling very sci-fi at the time...

I am an undergraduate researcher and my university had an SEM donated to us by DOW chemical. It since has been without power and we have to bake the column and the gun chamber. Contacting the company they estimate $17k to send someone out to do it for us. I'm having difficulty finding material...

Basically I want to build a notional interstellar drive its very powerful and scales up in efficiency and size at the same time I am 90% done and would like to hear what you all think. Start with a hydrogen oxygen torch Pump up the flame with a microwave beam Feed the plasma into a particle...

Is the idea of negative absolute temperature analogous to a virtual image in geometrical optics? I was reading this article about such a negative temperature: http://www.livescience.com/25959-atoms-colder-than-absolute-zero.html It seems to me that since temperature is defined by its...

1- I am trying to understand the rotational motion and In most books there's ##\vec θ## unit vector which its, ##\vec θ=(-sinθ,cosθ)## I can see that If ##\vec r## unit vector is,##\vec r=(cosθ,sinθ)## then , ##\frac {d\vec r} {dt}=\vec θ## Like calculating ##\vec v=\frac {d\vec r}...

Ok. So while in my trig class, I had an idea for a ball point pen that, when writing, it has an automatic mechanism for making dashed lines. I mean to say, it lifts the ball point or obscures the path to create a perfect dashed or dotted line, or allows to draw a line of fixed length for...

I've been considering a degree at the UAM due to the fact its incredibly cheaper than in the US. Any thoughts if this is a good idea?

Hello,I know how to use latex, and some how I want to write that in my CV, but its really unprofessional to do that! so I am thinking of writing my CV and my personal statement instead with latex, and so if someone is interested in such a skill (Which isn't that much of a thing) he will notice...