Speed Definition and 999 Threads

To measure the two-way speed of light, a pulse of light is sent thru a vacuum to bounce off a mirror and return. By knowing the distance to the mirror and how long the pulse takes to travel, the two-way speed of light can be calculated. To measure the one-way speed of light, place a transparent...

Let’s assume a world where it is secretly revealed that traveling West to East there is speed of light instantaneous, and in the reverse direction a c/2 velocity . Now let’s assume this applies to an arbitrary point in space and east and west assume are linear flat Now …. Let’s assume there’s...

I tried drawing the wave, counting 3 meters (speed is 1 meter/s) and bounced back from the stationary point (at 5) when necessary. Using this, I found the answer to be drawing 2. Wondering if that's correct.

Some of the power performance parameters of an electric car are shown in Table 7-1. If the car starts from rest and moves along a straight road with a uniform acceleration of a = 1.5 m/s2, when the speed reaches v1 = 72 km/h, the motor works at the rated power, and the power of the motor remains...

Since "Space" is just a Distance between 2 objects , isn't "Space" just equal to Distance ? If so , then the term "SpaceTime" can be called DistanceTime . Which I think clarifies what is meant . And I think it's meaning is thus a Distance Time . In other words , it just refers to the TIME it...

So an extreme case ….. A cluster of matter and space, in direction of motion will be to us a huge huge disk with thickness of say 1 millimeter due to length contraction , traveling straight past the earth at velocity essentially c (very very very very close to c) However, relative to this...

Hi. To my understanding, the mathematical justification of various superposition principles in physics is that the sum of solutions to a linear differential equations is again a solution to the same equation. This justification works for solutions of the wave equation...

Theoretically, if a person falls from outer space to earth, and they hold 10000 rolls of toilet paper by their loose end, will that slow their fall down? Can you do that with a rocket booster returning to earth, keeping its speed subsonic all the way? On more serious note, what happens if you...

C2 means the speed of light squared so Mass traveling at the speed of light times itself becomes energy. That would mean we could travel up to.34,500,000,000 miles per second before breaking down into pure energy. So we should be able to travel faster than the speed of life. Did I miss something?

If two seperate, coherent light beams were to intersect at a slight angle near the viewer, and then very rapidly made parallel,could the intersection point move away from the viewer in excess of the speed of light? If so, could that intersection point be made visible somehow,and how would the...

Everything has the speed it's moving at , at the time it's measured . Light always leaves its Source at the speed called "c" . That doesn't mean its Relative speed is always "c" for all observers .

https://www.technologynetworks.com/neuroscience/news/caltech-scientists-have-quantified-the-speed-of-human-thought-394395 So there you have it! We humans think at 10 bits per second, slower than a slow-moving locomotive, slower than a 1960s Model 30 teletype, and slower than molasses. It's...

Motion is probably not the right word, maybe perception. I was thinking one day about the speed of things and came upon a question I couldn't answer. So you have two people on either side of a valley, person #1 claps their hands. That sound reaches person #2 in X amount of time. Person #1 then...

Is there a temperature-change equivalent to the speed of light?

...but is it correct to say: Speed² (in space) + Time² (in space) = 1 ?? derived using Pythagorus (explained at 10-13 minutes in)....the trade off between Speed and Time, at maximum speed Time is zero and at max Time, Speed would be zero.

Hi PF, as far as my modest knowledge goes, measuring the one-way speed of light is impossible / non-sensical (?). Thus I'm not here to actually propose a possible method for that purpose, but I just would like the savvy among you to point out the fallacy in my reasoning. That said, I was...

Would a gravity powered clock increase or decrease speed? Take an hourglass. It should increase speed as gravity increases because it's powered by gravity... But it should also decrease speed because of general relativity...

Like, i don't even understand what it means by the ball accelerating at 0.5m/s2. is it accelerating upwards constantly at 0.5m/s2? what about gravity? the answer given is weird. initial speed u = 5m/s and t = 10s it says time taken to go up is = time taken to go down. (why?) so total time...

How can an approaching observer receive the information from a source at a higher rate (as an accelerated recording), while the information-carrying radiation could not?

If I stand by a flying with constant speed charged particle, at my location the electric field will change as the particle get closer and further from me. So this change in electric field should create magnetic field and so on, producing an EM wave?

How can the speed of light remain the same for an observer while the duration of a light beam is shorter if you move towards the light, and longer if you move with the light? The light beam remains the same length.

Looking to see if I am in the ballpark correct about this. Let's say a spaceship flies at 99% the speed of light (B=0.99) to a planet 12 light years away. The spaceship is going to land on the planet once it arrives and stay put ever after. Ignore acceleration of start/stop. When it lands on the...

So far I've got: ##p_{1,i} + p_{2,i} = p_{1,f} + p_{2,f}## ##p_{1,i} + 0 = p_{1,f} + p_{2,f}## ##m_1v_{1,i} = m_1v_{1,f} + m_2v_{2,f}## According to the textbook, the final speeds should be written in terms of ##v_{1,i}, m_1, and m_2##. It looks like I need another way to relate everything...

I understand that if the sun where to 'disappear' then it would take several minutes for the us on the earth to notice as the light takes time to travel. Does this mean that it would also take the same time for us to notice that the gravitational (or electromagnetic) force would disappear too...

i got confused because if the connections btw the parts

This is not homework, it's a problem I came across while trying to model differential braking for my flight simulator. I cannot really see what force pushes the vehicle horizontally and I would really appreciate a detailed explaination.

my question then is that can we ascertain some unknowns about the physical constants of our universe by using video altered speeds , to observe the universe through moving picture frames ? Is there a project benefit in doing more with this ?

I read on the forum that: "Michelson-Morley results strongly suggested the local speed of light being the same in all reference frames." I think that's an erroneous understanding. MME only suggested that there is no ether because speed of light is not affected in any direction and remained the...

My query is on highlighted. This was straightforward. I thought that coefficient of friction ought to lie between ##0## and ##1## maybe i need to check that again anyway; ##F_{lim} = 1.5 ×15000= 22, 500 N## Using ## v^2 = u^2 +2as## and ##F=ma## ##22,500 = 1500a##...

If I’m not mistaken, the synchronization of 2 clocks to conduct a measurement of the one-way speed of light is not possible since simultaneity is not possible and 2 clocks even if they are synchronized in a midpoint and slowly moved to opposite ends, depends on c being the same in all...

I am interested in making an observation that involves the speed of light. It is widely stated that the speed of light is constant, but without saying what that means. I need to be precise, and would like a reference to an acknowledgement of the problem. When people talk about the speed of...

As part of an audio-visual I'm producing, I want to video two passing road signs while driving in a car on a country road. The videos have to fit in with commentary and music, so the timing is pretty tight, and I want to get it right the first time I visit the area – 4 hours drive from home...

Hi. According to Wikipedia: The "one-way" speed of light, from a source to a detector, cannot be measured independently of a convention as to how to synchronize the clocks at the source and the detector. Mid 20th century, the most precise measurements of the speed of light were done using...

For this problem, My working, (a) ##d = a~ly = ac~y## ##v = \frac{d}{\Delta t} = \frac{ac}{b} \frac{m}{s}## (b) Lorentz factor is ##γ = \frac{1}{1 - \frac{a^2}{b^2}}## Thus time dilation is ##\Delta t = \frac{b}{1 - \frac{a^2}{b^2}} y##, however, I think my arugment is only valid if ##a >> b##...

For this problem, My working is (a) ## \Delta t = \frac{a}{\sqrt{1 - b^2}}~ns ## (b) ## \frac{abc}{(1 \times 10^9)\sqrt{1 - b^2}}~m= d_1 ## (c) By symmetry, ##d_2 = -d_1## ##-\frac{abc}{(1 \times 10^9) \sqrt{1 - b^2}}~m= d_2##, however, I'm not sure whether my explanation for (c) is enought...

Does the product of Planck's Constant and the speed of light, hc, have any significance in physics other than an arbitrary product of two constants? I noticed that it appears in one formula for the fine structure constant. It also appears in Planck's formula for black body radiation. Thanks...

Hello, In this study https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9784821/, the distance the punch travelled from start to impact is 0.49 meters and the time taken from start of punch (that's it, they define the start of punch as the moment the elbow first start to extend) to impact is 0.1...

Is there an explanation for why the speed of light tops out at 186,282 miles per second? Of course that number depends on our definition of miles and seconds. If a mile was 3000 feet then c would be a different number. But whatever speed it is…. Why that speed? In other words… there is...

TL;DR Summary: This is an astronomy application. Mentor note: Moved from a technical forum section, so the homework template is missing. How long does it take a beam of light to reach Earth from the Sun when the Sun is 93,000,000 miles from Earth? Express your answer in seconds, using...

TL;DR Summary: This is an astronomy application. One light-year is defined by astronomers to be the distance that a beam of light will travel in 1 year (365 days). If the speed of light is 186,000 miles per second, how many miles are in a light-year? Express your answer in scientific notation...

Ok, I took like a class in physics in college. It was a class to learn physics for majors that we really didn't care. I remember him saying, if you remember anything from this class, remember inertia. That's about all I remember from the class... lol. But, I don't understand why it's...

Hi. The numerical value of the speed of light ##c## pops out as propagation speed of the wave solutions to Maxwell's equations. It seems like everywhere else we need to plug in ##c## as a parameter. Why is that? Is there a way to "derive" the numerical value of ##c## in other theories, that...

I don't know how to explain it in terms of speed. I know the speed will decrease but if the ray entering the glass at certain angle, let say 10 degrees, the speed will also decrease so what is the relation of speed to the fact that the light will bend or not when entering the glass? And the...

my answer = F = 1.6*9.81 - 1.2*9.81 = 3.924 N -> resultant force of the drone moving (weight minus the upward force) M= 1.2kg , mass of drone a= 3.31 m/s^2 , acceleration of drone u=0 m/s , initial speed of drone t=1s , time v = 3.27 m/s, final speed of drone and its not even in the options... 😶

Can someone explain to me what I am doing wrong? Trying to calculate the Temperature T using this formula I am trying to find T using most probable speed of atoms formula. T = (V^2) m/( 2k) I am getting riduculous T like 20x10^27. Why? If number of atoms N= 2x10^24 how do i get mass m? each...

I have been taught that speed of pulse is v = √(T/μ), but here tension varies at each point therefore I cannot just simply apply the formula. I think integration would be needed, I tried but ended up nowhere. Can someone help me find the time?

$$K_i + U_i = K_f + U_f$$ $$K_i = \frac 1 2 m(15)^2$$ $$U_i = 196m$$ $$U_f = 0$$ $$K_f = K_i + U_i - U_f$$ $$=\frac {15^2} 2 m + 196m$$ $$=\frac 1 2(15^2m + 98m)$$ $$=\frac 1 2m(15^2 + 98)$$ $$=\frac 1 2m(323)$$ $$=\frac 1 2m(17.97)^2$$ $$v=17.97 m/s$$ Not seeing where I'm...

Sorry, I guess I should have remembered all of this from my school days, but right now I have forgotten so much that I need some help. I am developing some simple experiments for school children (age ca. 12). This one involving magnets. I am not asking for detailed calculations, that is way...

In the images you can see what I did I need someone to check answers and show me how to do C part of question