Laws Definition and 1000 Threads

How would the laws of thermodynamics change in a contracting universe? (Of course we live in an accelerating and expanding universe. So the questions are hypothetical.) On the internet, I get different answers: Most say that entropy will still increase or stay the same, but no explanations or...

I have tried the following. Firstly, we can write the law of conservation of impulse m1*v1 = m1*v'1 + m2*v'2, that is the first equation for the system. Then we can write the law of conservation of energy, like KE1 + KE2 = PE1 + KE'2, and then we can substitute formulas, but as far as I can see...

I used Snell's law to find θ2 as 40,1 (3sf) but now I'm stuck on finding θ3. Is there a way to find θ3 without using geometry? How do I do this?

TL;DR Summary: orbital speed laws I would appreciate a bit of explanation on how did we find e1 and e2 and if there are any useful references to learn about Kepler laws since I am lost for the most part, and would like to gain understanding and solving ability ,and if you can go into some...

I hope to have a nice time in the physics forum. I am interested in much about the laws of physics with respect to our daily lives and hope to achieve more and increase my knowledge in physics with the physics forum. Thank you for accepting my registration.

Hi, I am wondering why reflected rays are not considered with lenses? If a Ray strikes a surface another is reflected off that striking point; however, this is not added when studying lenses, only refracted rays are considered. Is there any law which gives the ratio of reflected and refracted...

The answer is 441N instead of 883N, but why? can anyone help?

Hello esteemed members, I have been studying some physics and I have the mentioned laws, but I have understood that the first law (elasticity modulus equals the stress over strain) ##e=\frac{\sigma}{\epsilon}## is valid only to limited range, and the second one is just a result of Newton's...

I've just seen a picture of a man being arrested in the US for not being fat enough. Incredible!

I was reading about the Tusi couple and read it "as a solution for the latitudinal motion of the inferior planets, and later used extensively as a substitute for the equant". Since the Tusi couple is related to plotting out an ellipse, did Nasir al-Din al-Tusi already discover the laws for...

Consider a fluid flow with density ##\rho=\rho(t,x)## and velocity vector ##v=v(t,x)##. Assume it satisfies the continuity equation $$ \partial_t \rho + \nabla \cdot (\rho v) = 0. $$ We now that, by Reynolds Transport Theorem (RTT), this implies that the total mass is conserved $$...

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In this popular science article [1], they say that if our universe resulted to be non-uniform (that is highly anisotropic and inhomogeneous) then the fundamental laws of physics could change from place to place in the entire universe. And according to this paper [2] anisotropy in spacetime could...

For curiosity (obviously not having anything better to do with my time) I turned my spectacles the ’wrong way round’ - so that they were upside down, with the arms pointing outwards - and looked though them. (This gives the correct lens for each eye of course.) The image is noticeably worse...

So on this page https://www.feynmanlectures.caltech.edu/I_11.html under heading 11-2 Translations first he tries to proof that there is no origin in space. Joe writes newtons laws after measuring quantities from some origin. $$m(d^2x/dt^2)=F_x$$ $$m(d^2y/dt^2)=F_y$$ $$m(d^2z/dt^2)=F_z$$ We need...

...y and Coulomb's law diverge as ##r\rightarrow##0? I mean, if a point light source emits light omnidirectionally, the intensity converges at the source, right? THIS is how I should've worded my previous post!

F parallel - F applied - rolling resistance = ma I don't know how to calculate for rolling resistance. If the bicycle is not slipping rather it is rolling, should I ignore rolling resistance? And if I ignore that I would get, F parallel - F applied = ma F applied = F parallel -ma...

How to find frictional force when coefficient of friction is not given?

If energy is "not conserved" in General Relativity (or at least, it is difficult to define it) in the context of an expanding accelerating spacetime (like it happens in our Universe), are there any observations of deviations from the strict conservation laws in the evolution and formation of...

It is argued that the correct interpretation of Newton's 2nd Law for one body of mass ##m## reads "The dynamics (i.e. vector sum of all external forces acting on the body = "all its interactions") dictates the kinetics (i.e. time derivative of the momentum vector = "motion")", under the...

I'm stuck to understand 3 laws of Newton. It doesn't make sense to me. 1. Suppose the case when a person stay in a rest vehicle.When we accelerate the car the person still at rest so the person has to move to the tail of the vehicle cause his intertia of staying rest. If we decrese the...

Hi. I have next task: Three current sources with EMF E1 = 11 V, E2 = 4 V and E3 = 6 V and three resistors with resistance R1 = 5 Ohms, R2 = 10 Ohms and R3 = 2 Ohms are connected, as shown on picture below. Determine the current strengths I in the resistors. Internal resistance sources neglect...

I was wondering if the electrical force, which is a radial force that depends on the inverse of the distance squared, also respect the Three Kepler Laws? If so, what will the constant for the third law be?

Hi, everyone! There are a lot of work energy conservation laws and I get confused which one of them summarizes all of them. Which one I should keep with me and rest should be easy to derive on spot ? 1. ##\Delta E_{mec}=0## 2. ##\Delta E_{mec}=W_{ext}## 3.##\Delta E_{mec} + \Delta...

The question is solved in a single step by taking the blocks as a system and using conservation of linear momentum in the horizontal direction as there is no net force acting in the horizontal direction. Conserving the momentum we get, m x v + M x 0 = (m+M)v', so,,v' = mv/(m +M).where v' is the...

Would you please explain how the laws of thermodynamics are related to one another? Are the laws entirely independent of one another? I can see only a connection between the zeroth law and the second law. Following is the quote from my previous thread. 1. Zeroth law: The zeroth law of...

how can l prove Newton's law is time invariant? if x (t) is a solution of dd/ddx x(t) = f(x(t)) then if l put y(-t) dd/ddt y(t)=dd/ddt x(-t). Now how dd/ddt x(-t) is equal to f(x(-t))?dd/ddt is second derivative with respect to time

Hello there, I have tried the problem but don't get a different of 6g's as I am supposed to. I am not sure whether I interpreted the problem in the correct way, but I would love some feedback/hints on what went wrong in my solution, thanks in advance. Solution: SITUATION DRAWINGS + FBDS so...

https://www.feynmanlectures.caltech.edu/I_10.html (From the paragraphs after equation 10.5) 'It is not just a definition to say the masses are equal when the velocities are equal, because to say the masses are equal is to imply the mathematical laws of equality, which in turn makes a prediction...

Hi, I have an interview for masters degree program in 2 weeks and they asked to study two subjects thoroughly, first being Hydrogen atom and second being Kepler's laws. anyone recommends one book about each subject with advanced level questions that would help me understand the subjects to a...

Here is the question: We know the equation \epsilon = \frac{d\phi }{dt} = BAcos(\theta ). This means that the only way we can create an induced voltage is if we change the magnetic field, change the area of the loop in the magnetic field, or change the angle between the normal vector to the...

I kind of just made up the questions. I realize this is a basic question but my knowledge of physics is very limited.q1 answer v_left_ball = v_left_ball - v_train v_right_ball = v_right_ball + v_train q2 answer To get the speed from Bob's frame I would use v_Bob = v_Bob + v_Alice To get the...

I am have some questions that have arisen while reading an old but interesting article by Andreas Albrecht [1] that cites an article by Andrei Linde in the 90s on cosmic inflation [2]...Albrecht's paper is related to his ideas on "clock ambiguity" in which he proposes that the laws of physics...

There are some theoretical processes (like vacuum decay in quantum field theory) that could change the physical constants of the universe. Similarly, in inflation theory, various models predict that multiple regions that would stop inflating would become "bubble universes" perhaps with different...

I have read a bunch of articles online regarding my question, and none have helped. Newton's Laws: 1. In an inertial reference frame, an object's momentum doesn't change unless acted upon by a force. 2. In an inertial reference frame, the force on an object equals the time derivative of its...

Does anyone know how to do part (a). I labelled the current through R1 I1, I4 through R4, I3 through R3, I2 through R2, and I5 through the 3ohm resistor. I used Kirchoff’s Laws to make the equations I1 + I4 = 8, 2I1 + 32I3 - 14I4 = 30, and I1 + I3 - I4 = 0. I solved these equations by subbing...

What is the difference of x->c^- and x->c^+?

Good evening! Have a look at the following part of a proof: Mentor note: Fixed the LaTeX I don't understand the use of implications. Isn't ##x\in C_M(A\cup B)\iff x\notin(A\cup B)##? To me, all of these predicates are equivalent.

News just in: Australia will introduce legislation requiring social media companies to reveal anonymous users who post defamatory comments. https://crsreports.congress.gov/product/pdf/R/R46751 has generally allowed US-based internet companies to avoid consequences for user posted content, and...

About 50 years ago, the San Diego Zoo, in California, had the largest gorilla on Earth: its mass was about 3.10 × 102 kg. Suppose a gorilla with this mass hangs from two vines, each of which makes an angle of 30.0° with the vertical. Draw a free-body diagram showing the various forces, and find...

I think you would do force of gravity= mass x acceleration acceleration of gravity= 9.8 m/s mass 75 kg 75kg x 9.8 m/s =735 N i don't know if that's right but i have no idea how to calculate it after he lands, any help would be greatly appreciated!

hello , I am adding pdf with the questions and what i tried to do to solve them. in the first question my teacher just taught us that if there is a frictionless floor and i push the upper block (m) with force F toward me then if the static friction will be toward me too. so the lower block M is...

I had a few questions about this paper by Nima Arkani-Hamed, Georgi Dvali and Savas Dimopoulos (https://arxiv.org/abs/hep-th/9907209) which is closely related to the concept of branes (https://en.wikipedia.org/wiki/Brane) 1. The authors of the paper mention that the branes in the model could...

I was taught that photons ( non-ionizing at least) never interact. So Its really bugging me that most info on faraday effect invokes B field as the cause of ( for example) rotation effects. Since EM-waves (IE Photons) themselves propagate a (oscillating) Magnetic field through infinite space...

Good day friends. I want to know and ask you if Newton's laws are incompatible with thermodynamics.

I tried to do it for 2+1 D (3+1 is done in the text, by writing the integral in spherical coordinates and computing it directly). In 2+1 D I wrote it as: E = - \int \frac{d^2 k}{ (2\pi)^2 } \frac{e^{kr cos\theta}}{k^2 + m^2} = - \int_0^{\infty} \int_0^{2\pi} \frac{d k d\theta}{ (2\pi)^2 }...

Hello All What would be the motion of a weight dropped into a hole drilled all the way through an Earth-sized planet? Would the weight accelerate all the way to the centre and then decelerate until it got to the far side, and repeat this motion forever? OR Would it accelerate initially and...

The phenomenon of diffusion is a transport phenomenon based on the thermal motion of molecules, a process in which molecules are transported from a region of high concentration to a region of low concentration by Brownian motion. Let's assume that there is a car, the road under the wheels is...