Classical Physics

Acceleration is velocity over time. Velocity is distance over time. So, acceleration is distance over time^2

Were the retina at the back of our eye like a concave mirror then is it possible the image would be reflected back out the converging lens (under the iris)? So the inverted image above is already formed in front of the retina (B’) and might essentially be re-inverted upright(B): https://www.teachoo.com/10826/3118/Concave-Mirror---Ray-diagram/category/Concepts/ Then the image might be re-magnified on attempting to exit back out the converging lens under our pupil to potentially create a virtual image in the eye to simulate the reality we see: https://www.teachoo.com/10838/3118/Convex-Lens---Ray-diagram/category/Concepts/#google_vignette …

Hi, new here, though most interested in physics and its elementary subjects. Have stayed around in physics sites at the internet since late 1990's. ~~~~~~~~~~~~~~~ And still the "universal" concept of "time" has never, to my knowledge, been satisfyingly explained in a physical and scientific manner. This may be caused by: 1. Time is a most enigmatic function/ behavior/ dimension in science. 2. People have cognitive difficulties in general which the concept of "time" is revealing. 3. Science and physics is generally a "young" human discipline. ~~~~~~~~~~~~~~~~ To my layman understaning one have measured time historically by thre…

-the heat of wood burning in a fireplace comes from the sun because of Lavoisier quote('nothing is created and nothing is destroyed but everything is transformed')... Is it true? If it's true it means that a tree removes heat from the environment as it grows, therefore the difference in the quantity of trees (wood...) means that there is more solar heat in the environment compared to centuries ago and it can justify global warming regardless of the presence or absence of CO2... Opinions?

One thing should be mentioned: Only the translational modes of molecular motion contribute to the temperature. Different substances have different heat capacities because they absorb energy in all their modes, but only the translational modes increase the temperature, thus the more modes that are available to the molecule, the more energy that is absorbed for a given increase in temperature.

I'll like to know the actual physical mechanism how matter absorbs EM radiation. Take the specific example how copper metal absorbs IR radiation and the copper having its temperature raised.

I do not know if this is the correct section? sorry if not and could you please tell me what branch i need. I have many "pellets" which are cone shaped. the rear is always 6mm in dia ,the front is 4.5mm. This 4.5mm size varies slightly in manufacture. it is very time consuming measuring with a digital caliper. i have seen a video on YT of a guy using a great method. the video is not great quality with no sound. what he uses is a raised piece of wood to form a ramp. he puts a pellet at the top corner and lets go. the pellet rolls in a arc. the pellets roll in different arcs depending on the size. he made little pots along the board edge to catch th…

My question is about the following step in a derivation of energy-momentum tensor: When the ∂νL in (3.33) moves under the ∂μ in (3.34) and gets contracted, I'd expect it to become \(\delta^{\mu}_{\nu} \mathcal L\). Why is it rather gμνL ? Typo? (In this text, gμν=ημν )

Is there a device you can buy that detects and measures ultrasonic sound? If so how much would i have to spend to get one? Any links to such devices? Thanks

Here are steps of derivation of energy-momentum conservation: Consider a shift of the field ϕ by a constant 4-vector ξ : (1) ϕ(x)→ϕ(x+ξ)=ϕ(x)+ξν∂νϕ(x)+... The infinitesimal transformation makes (2) δϕδξν=∂νϕ and (3) δLδξν=∂νL Using the E-L equations, the variation of Lagrangian is (4) δL[ϕ,∂μϕ]∂ξν=∂μ(∂L∂(∂μϕ)δϕδξν) Using (2) and (3), (5) ∂νL=∂μ(∂L∂(∂μϕ)∂νϕ) or equivalently (6) ∂μ(∂L∂(∂μϕ)∂νϕ−gμνL)=0 The conclusion is, "The four symmetries have produced four Noether currents, one for each ν : (7) Tμν=∂L∂(∂μϕ)∂νϕ−gμνL all of which are conserved: ∂μTμν=0 ." My question: …

Checking with the physicists here: On the p.17 it says, Shouldn't it say force rather than potential? Isn't any potential rather quadratic close to equilibrium?

I merged two formulas for Force I saw in a video. First - Did I do it right? F = ma= (G*M1*M2)/R2 1. F = ma 2. F = G M1M2/ R2 Second- If it is right does G/R2 represent the acceleration part of F= ma ?

Could you take alpha radiation and then strip the neutrons from it using gamma radiation and then apply radiation to heat the proton pair to lead to fusion?

Is there a metal out there you can bombard with electrons to get gamma radiation?

I read that Earth would have to spin at 28,437 km per hour to cause us to lift off the surface. I’m assuming at that point we would effectively be weightless. Seemingly throwing a wrench into F=GM1M2/R2 , so what effect would it have on the moon?

Entropy is a measure of the disorder of a system. The higher the disorder in a system the higher the entropy. In terms of matter there is more disorder in gas state then there is in solid state. As entropy indicates disorder or randomness of a system it also takes more information to describe higher entropy system. It would take less information to describe the structure of matter in solid state then in gas state as solid state is way less disorderly .So the higher the entropy is the more random it would be and the more information it would contain .As such entropy would be proportional to information If we take entropy as being proportional to information then infor…

The Navier-Stokes equation is solved in a vector grid in a Cartesian coordinate system. That is, rectangular. But does a rectangular mesh relate to what happens in a gas or liquid, and is it better to use a triangular mesh? Undoubtedly, it is incredibly difficult to take into account all the factors even in a triangular or tetrider coordinate system, which is difficult even for visual perception. And in its direct form such a solution is impossible. But it is precisely this system that allows the logical formation of figures that we can see in water - a ring vortex or torus, similar to a figure eight (infinity) and a hexagon, similar to a snowflake or polar vortexes …

Information entropy is a concept from information theory. It tells how much information there is in an event. In general, the more certain or deterministic the event is, the less information it will contain. More clearly stated, information is an increase in uncertainty or entropy. If we take entropy as being information then information is not constant as Entropy is not constant. The Second Law of Thermodynamics states that the state of entropy of the entire universe, as an isolated system, will always increase over time. If Entropy is increasing then information in universe is also increasing. Let's say it is Quantum mechanics for which information i…

Can you please help me figure out how this toy works? I realized that it is kind of wound up and it, accordingly, spins. But please help me to understand this question in more detail. Perhaps someone has some ideas? I would be very grateful. I would especially appreciate diagrams.

Well they do not do this, never did. So why when this was said didn't the physicist who designed the ovens put a stop to the rumor?

Hello. I am a high school student with only a bit of knowledge of physics that I picked up from a few textbooks, and god knows where. I've been thinking about hyperbolic planes and the field of physics. Like what if hyperbolic planes have something to do with some of the forces we have in the universe? What if the electromagnetic field (example) is a hyperbolic plane that expands past the euclidean plane, what would that look like? Am I stupid? If so, please don't insult me. I'm just a high school student who's very interested in the topic of science and doesn't really have much to go off of. If not, I wonder if there's some studies on this I could check out, and perhaps …

Imagine painting a mirror and then beaming a sun-like spectrum at it. Will that still reduce the heat-producing IR wavelengths passing right through to the other side? What I'm thinking is, if you papered the ceiling with mylar material and painted it, could that improve insulation?

I read on Wikipedia that a hologram is made by superimposing a second wavefront ("reference beam") on the wavefront of interest, thus the image "animates" when moved. I would like to know if more than one wavefront can be used, to create a smoother or more complicated animation ?

Dear physics geniuses, I have a situation that I need help with. There is a van on the street and someone took a photo of it. I have uploaded 2 photos here What I need to know is how far is the top of that white hinge from the ground (so the distance between the red line and the ground) and how far is the bottom of that white hinge from the ground (so the distance between the green line and the ground). Some information that might be helpful: This van has a California license plate. in California, license plates are 12 inches by 6 inches. The van is a Ford Transit 150. I don't know what year. I don't know how far the camera was from the …

So, I was playing around with SI units and came up with the equation in the picture. where v is velocity, F1 is the force exerted on an object, m2 is the mass of the object the force was asserted on and d2 is displacement. Let me go through how I came up with this. First, I broke down force into its base components. A newton is equal to one kg*m*s^-2. So, I divided it by kg to remove the kg on the top. We are now left with m*s^-2. This is almost velocity but not quite. So, I squared it, so it is now sqrt(m)*s^-1. I just multiplied it by m to get m/s. Just to avoid confusion, kg is weight, m is length and s is time. So, I put this into an equation and suddenly I…