Speed Definition and 999 Threads

[Moderator's note: Thread spun off from previous thread due to topic/forum change.] Time dilation sounds really weird, can i assume it has a logical explanation?

Two clocks with photo detectors are 100 kilometers apart at A and B. On the center of AB axis two light pulses are sent to the clocks , synchronizing them. Then a light signal is sent from A to B. The two stationary observers record the time from event at A to event at B. Is there a one way...

Sorry for the bad english. This might sound stupid but I am pretty new the physics and i can't seem to find what formula to use on this problem when only the mass, gravity and height of the fall is given. and i can't find a similar problem in the book, could someone give me any pointers? Thanks...

First off, I'm probably totally incorrect on all of this, so feel free to correct me. Second, I'm only 15, so please just be gentle and helpful when I'm totally off. Now for my idea: Have a huge vacuum and put lasers on the inside with hundreds of different lasers at different angles equally...

Hello there, I believe here I need to find the capacitance of the junction between the P-doped gate and N-channel. Then I could find the RC time constant although I am not sure if there's something more I need to find the speed of the JFET? What I'm unsure of is the depletion width h to use...

Hi. I cannot find the correct answer to the problem. Attempt: Net Fx = T - Fg - fk = 0 Fk = 0.16(mgcos30) = ma a = 1.3579 m/s^2 v^2 = u^2 + 2as v^2 = 0 + 2*1.36*4.3 v = 3.417 m/s Answer: v = 3.9027 m/s What did I do wrong here?

Why are gravitational waves able to move at the speed of light?

I was doing a exercise which considerst he time it takes for light travels a glass with thickness proper D and velocity v. The speed of light is c/n inside the glass. Now, my approach was to go to the glass frame, take the relative speed between the glass and the light using the trivial formula...

I am an amateur in physics and I have a question. How does speed of an object affect time?

I don't really understand the question. A proton collides obliquely with another proton means that the first proton moves at certain angle with respect to horizontal? This is my sketch: Is that correct? If yes, is it solvable since there are so many unknowns? Thanks

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I know it's not possible to travel at light speed so this is just theoretical. As I understand it at relativistic speeds the distance you need to cover to travel to a destination are length contracted. If you were traveling at light speed is the distance between you and any object ever zero?

“incidentally, to a good approximation we have another law, which says that the change in distance of a moving point is the velocity times the time interval, Deltas=vdeltat This statement is true only iF the Velocity is not changing during that time interval, and this condition is true only in...

Hi everyone! :) While i watched rc jet exhibitions on youtube, i find that the most fast of this RC reached +700 Km/h. When i browse more information about the tourbine, i realized that for a hypothetical supersonic RC the mechanical system of the tourbine must have a complete air compressor...

"We know only where she was at intervals of one minute from the table; we can get a rough idea that she was going 5000 ft/min during the 7th minute, but we do not know, at exactly the moment 7 minutes, whether she had been speeding up and the speed was 4900 ft/min at the beginning of the 6th...

There was a lot of kerfuffle a decade ago about neutrinos possibly exceeding the speed of light, A re-analysis of events debunked this back in 2012 I believe, but I don't know if the issue is conclusively settled. Has there been any re-confirmation of the speed of neutrinos in any paper later...

Consider the situation where an observer at rest on the ground measures the frequency of a siren which is moving away from the observer at speed ##v_{Ex}##. Let ##v_w## be the speed of the sound wave. Let ##\lambda_0##, ##f_0##, ##\lambda_D##, and ##f_D## be the wavelengths and frequencies...

We know the speed of light is a constant but speed is just the measure of distance over time. If blue light has a shorter wavelength than red but covers the same distance / time does this mean that blue light has actually made a longer journey than red light in order to arrive simultaneously? I...

Some people thought light speed is actually instantaneous which can be demonstrated by doing an experiment involving a taut clothesline and two clothespins. On each ends of the taut clothesline, put one of the clothespins on both ends and touch one of the clothespin will make the other one at...

I've written in that only the first statement was False, however my classmates aren't getting the same answer? Please help clarify...

As an object approaches a black hole’s event horizon, it experiences increasing gravitational time dilation, causing it to appear to an outside observer to slow down, until, at the event horizon, it appears to stop. An object traveling in space that increases its velocity from one...

In Richard Feynman's book "The Strange Theory of Light and Matter", in chapter 2, he explains how to calculate the probability that light from some source will be reflected by a mirror and be detected at some location. He explains how you sum up all of the probability amplitudes (represented...

I have attempted a solution using conservation of momentum. Could people help check if this solution is correct (the result looks weird), as the problem doesn't have solution with it. $$ \begin{aligned} \begin{pmatrix}Mc \\ 0\end{pmatrix} &= \begin{pmatrix}E_R/c \\ \mathbf{p}_R\end{pmatrix} +...

The universal speed limit is c, and as a consequence light is confined to that limit. I was thinking about the time dilation in SR and was wondering if this is result of reaching speeds close to the speed of light or because of reaching speed close to c? For example, let's say light could be...

The question is simple. The molten stuff inside the Earth will get a smaller volume when it solidifies. Will the Earth increase its rotation speed in reaction to this? What about the magnetic field?

I watched a Fermilab video on light propagation in water: . He says (~) at time 7:50: "The oscillating electric field of the light make electrons in the glass move. These set up a second oscillating electric field that combines with the first to make a single oscillating field. That is the wave...

This is one of my thought experiments where I am drawing a big blank, If you have 2 objects approaching a 3rd object from opposite directions (just enough off to avoid collision) at 75% of the speed of light, the first assumption is that each observing the other would see the other object...

Hi, I'm working on a project to see if deliveries, pick ups, or both combined are better for the environment / more energy efficient / more time efficient. For example, (a) everyone collecting from a farm by bike, (b) vans bringing to supermarkets and then people collecting from supermarkets, or...

I am not able to understand the following paragraph from my Physics textbook;

I am an Engineer, so I have some knowledge about physics and calculus. I've seen relativity in university years ago but only briefly. The majority of my knowledge in SR and GR, which isn't much, are from reading, studying and searching online myself. I have seen some definitions that I am not...

Since an object's apparent mass increases as it approaches the speed of light, does it's gravitational forces also increases? (From a stationary observer's point of view)

I don't need equations, I would just like to pose a question which contradicts the above statement (I know I am wrong btw, I want to see where I am going wrong).My understanding of space (not near any gravity and therefore no spacetime curvature) is that a body in motion will continue to move at...

This looks like a physics question but it's not; it's an automotive question. Suppose you had a car at the top of a gently sloped hill, a 5% grade. You start it and put it in neutral or drive and it starts to roll down. You never place your foot on the brake or the accelerator and suppose the...

Can time dilation vary without a gravity well or accelerating a viewer towards light speed? Are there other variables that affect the flow of time?

**My Attempt:** Here, I considered for 2 kg mass the resultant motion is zero, which means it's acceleration (a) would be zero. So, if we consider the Tension force from the 1.5 kg mass to keep 2 kg mass from falling is L, then 2×9.8-L=ma=2× 0 ⇒ L=19.6 N. But where does the tension force from...

a. To find the speed, I need to find the height where the cords first become loose, which is when the cord is 25 m long. $$h=30-\sqrt{25^2 - 5^2}$$ But the teacher's working is ##h=30-\sqrt{25^2 - 4^2}## How to get 4? b. My idea is to use Newton's 2nd law so I draw free body diagram of the...

I have several confusion about this question: 1) Since the sand spilling out downwards, it means that there is change in momentum in vertical direction (before the sand spills and after the sand spills) but no change in momentum in horizontal direction so no net force in horizontal direction...

Hey dear physics community :) I ask myself what exactly happens to forces between materia when the materia hits near lightspeed. I know, that for an objective bystander watching let's say elon in his rocket with 99,99999% the speed of light, that the time goes slower, the mass of the rocket...

If a spaceship travels near the speed of light, could the frequency of cosmic background radiation blue-shift?

I have no problem in following the literature on this, i find it pretty easy. My concern is on the derived function, i think the textbook is wrong, it ought to be, ##S^{'}(t)##=##\frac {4t} {\sqrt{1+4t^2}}=0## is this correct? if so then i guess i have to look for a different textbook to use...

Though average speed over a finite interval of time is greater or equal to the magnitude of the average velocity, Instantaneous speed at an instant is equal to the magnitude of the instantaneous velocity at that instant. Why so?

Nevermind I found what I had to do, thank you though.

qn3: why is statement 2 the only answer? isn't speed one of the factors in velocity too? then shouldn't statement 1 be true too?

To an average person with high school math knowledge how would you explain in a few words why no object could travel faster than the speed of light ? Well it's because...

Derek Muller is the Veritasium YouTube channel host and he had a wager against UCLA professor Alexander Kusenko on whether a unpowered car going downwind can go faster than the wind. Derek Muller said it can go faster than the wind, while Alexander Kusenko said it only seems that way because...

Summary:: Question: a car of mass 800kg, 3600N driving force experiences resistive forces of 120v Accelerates from rest. Form equation and show max speed is 30 ms^-1, assuming driving force does not change. my attempt at a solution -I can not see how to rectify it as I don’t think I did...

I would like to know how to calculate, for any specified frequency in Hz, the required diameter of a 90 degree phased, quadrature coil array such that its generated EM field achieves rotation at the speed of light. Could someone please provide an example of the calculation using a specific...

I was discussing stepper motors with a friend. We touched upon different aspects. I showed how the coils in the motor have a limit to how fast they can be fully saturated with current, and how this time can be calculated by the aid of Kirchhoff's and Lentz's law. The theoretical speed calculated...