Speed Definition and 1000 Threads

The wavelength of light from a moving source is red shifted which means that the wavelength has increased and the quantity of energy arriving per second at a relatively static destination is less than the quantity of energy emitted per second at the source. If so then the original quantity of...

A train is traveling around the Earth at just under light speed. Light would circle the Earth around 7 times per second so let's say this train cricles the Earth 6 times per second. There is a physical ticker on the track of the train that records revolutions. Each time the train makes one...

The given solution is: However, I could not agree this solution, and my solotion is: So which one is correct? it seems a exponential decay would be more convincing. Thanks!

My approach: Assuming non-relativistic velocity: $$p = mv$$ $$mvL = \frac{\bar{h}}{2}$$ $$v = \frac{\bar{h}}{2mL} = \frac{h}{4\pi mL}$$ $$v = (6.626*10^-34) / (4pi * 1.67*10^-27 * 4.3*10^-15)$$ $$v = 7.34*10^6 = .0245c$$ This answer is incorrect. What have I done wrong? --- Edit: My...

At the risk of sounding stupid, this question has always perplexed me. Einstein theorized that mass can not travel faster than the speed of light. I don't really understand it, I assume it has something to do with mass just being energy. Anyway imagine two objects in orbit of something with...

Before I have read Bernoulli's theorem I believed that pressure is more in liquid flowing with more speed but today I have read Bernoulli's theorem where this theorem says that the pressure is more in liquid flowing with lesser velocity please tell me how can this explained,with equation I...

It is well known that relativistic speed addition is a non-commutative group (gyrogroup). The addition of two orthogonal speeds is given by : ##\vec{u}\oplus_\perp\vec{v}=\vec{u}+\sqrt{1-u^2/c^2}\vec{v}## Hence if ##u## is describing a photon with speed c then we can add whatever ##v## it...

$$ H = \frac { V^2 - V_0^2 sin \Theta} {-2g} $$ $$ H = \frac {V_0^2 sin \Theta} {2g} $$ So, I need to calculate ## V_0 ## I'm thinking about pressure. $$ P = \rho g \Delta h $$ $$ \Delta h = h - L sin \Theta $$ $$ F_A = P S_A $$ $$ F_A = P S_B $$ Dead End here...

Sorry if this is a stupid question but I couldn't find an answer anywhere. According to 2 scientific papers, the neutron star PSR J1748-2446ad has a rotation rate of 716Hz, which equates to a linear surface speed of 0.24c. What if this star was originally rotating, let's say, 5 times (or more)...

Current is determined as the amount of charge moving past a certain point of reference (like the point in a wire with current meter clamps around it) in 1 second. This got me thinking , so in a classical resistive load situation with Ohm's law there would be two ways to increase the amount of...

I know we end up with ##c=\sqrt{\frac{1}{μ _0.ε _0}}## The reason I would like a bit of help is that I understand that the value of c as deduced from Maxwell's equations is independent of any frame of reference. I can see that this is the case from the above equation involving the...

In relativity, the speed of light in vacuum is a universal constant. Also, it has wave-particle duality. So if the speed of light slows down in a different media other than vacuum, what exactly is slowing down? Macroscopically speaking, the speed of light does slow down. What about in the...

If we’re looking through a telescope at a craft we launched from Earth that is now passing Mars and send a radio signal to our craft telling it to turn on one of its lights on and it takes thirteen minutes for the radio waves to get from Earth to our craft how long will it take before we see the...

Okay, having devised the antimatter bomb, I'm moving along to the concept of using Apollo group asteroids as freight trains for the inner solar system, but my knowledge of orbital mechanics is zilch. For example, (343158) 2009 HC82 appears to have a max speed of about 56 km/s at perihelion...

we have a pick & place application so please give the solution for that data cylinder stoke length 200mm, travel distance 200mm ,what is the picking time?

So, pretty much I want to make an experiment in order to get the speed of light. What I plan to do is to have a lantern in the dark(initially off) perpendicular to a wall, two sensors(one closest to the lantern and the other closest to the wall), then turn on the light making sensor 1 go off as...

Why is speed of light in matter medium smaller than speed of light in vacuum?Are all photons must be absorbed by atoms and then the atoms re-emit radiations in matter?What is real picture of all photons in transparent medium?

Is instantaneous limited to our in ability to continue to count time faster.

Summary: Will the motion around us become faster when we travel faster? When we approach a body rotating on its axis with certain speed v, will we see the body rotating in speed slightly more than the v during our motion ?And what happens assuming that we are approaching the same body in speed...

Hi, I'm struggling to solve this problem. Can anyone please solve it and explain it to me? Thanks.

Summary: Is it the same as Bohm velocity ? Is it the same as Bohm velocity ?

Hi everyone, The equation is one we have been given to calculate the rotational speed of the sun for different latitudes. phi = average latitude. This shouldn't be a problem for me, but for some reason I just can't trust my error calcs. We are given : A = 14.713 ± 0.0491◦/d B = −2.396 ±...

Hi, As the summary says, I'm trying to design a simple gearbox with an approximate ratio of 20:1. I have two preliminary designs, one using a worm gear and another using a train of 5 spur gears. Both designs give me the desired ratio, but I really don't know which one I should choose. The...

We can calculate the average speed using this formula: uavg=root(8PV/ΠnM) I plugged in the following values: P= pi*10 atm (bar is approximately equal to atm) V=8lts n=2mol M=32*10^-3kg/mol But it is giving wrong answer. Can you tell me what went wrong?

For part a I used conservation of energy. -m*g*cos(θ)*L+1/2*m*0^2=-m*g*L +1/2*m*v^2 => v = sqrt(2*g*L(1-cos(θ )). b) For b I was think that T = mg in the equilibrium point but that doesn't invole θ in the answer. So that's why I tought that T*cos(θ ) = mg. So that the tension is mg/cos(θ). But...

Hi. I am new here. I have a question on how to speed control a DC motor running a pump. The pump is a seawater cooling pump cooling a large V8 motor. Therefore I need to control the RPM, based on the temp of the V8 Motor. Any ideas?

Summary: What if the Earth would have spin around itself twice as it's speed? What would have be the consequences? How would has it affect the climate and living things?

What about if the speed parameter in a Lorentz boost were in fact related nontrivially to a Galilean speed ? More formally ##L(v_L)=G(v)\circ F## where L is a Lorentz boost with Lorentz speed ##v_L##, G is a Galileo transformation with speed ##v## and ##F## is still an unknown linear...

I heard that the speed of light doesn't depend on the wavelength or frequency of it, how does it happen? I don't understand it because the ultimate equation is c = fλ (where c is the speed of velocity of light, f is the frequency and λ is the wavelength of it...).

Hi all, so I had this problem and on the exam and I got a solution but I had an mass-term in there which wasn't given. I used Farraday's Law of Induction to get the Voltage induced. Then I used ##rho* \frac{A}{4a} ## for the resistance and divided the Voltage by that to get the current. I then...

Hi, I found a programming problem that calculated the speed between two cars as below and I would like to know how the calculation is done. it is about determining the speed of two cars. The coordinate reference system (y,x) is attached to the ego vehicle (as shown in the attached figure). The...

Hello People, Greetings! i am back again with a confusing question for which I thought I could get a correct answer from here. so my question is regarding the speed of the turbine. I learned that the speed of a turbine has to be maintained constant in order to maintain generating frequency...

I am trying to get the real object speed at a current moment. The movement is circular. I have all the timings. This is the data, the speed is in milisecounds, and the numbers represent the revolutions: 1. -504ms 2. -720ms 3. -1044ms 4. -1332ms I know the average speed of the object, at...

Summary: Why is the speed of light limited? Why does light have a maximum speed?

First some basic figures which are very rounded as I'm interested in the approach to the problem rather than accuracy of the answer at this stage: The field current will be 500/220 = 2.2727 Amps, and so power is a fixed loss at 1136.36 Watts The armature current is 45 - 2.2727 = 42.72 Amps. At...

Let's say I can see a star in a distance of 1ly in front of me. I'm sitting on an office chair and begin to rotate with a speed of 1/s (1 rotation per second). Then I consider me as not rotating and everything else as rotating. Now I will see the star traveling a circular path with the...

Hey everyone I'm struggling on the last part of this assignment. I need to find the total work done by the block and the bullet, when the collision happens. The informations is: mblock=0.3 kg mbullet=0.01 kg vg=700 m/s Height=0.72m The final speed after the collision is vf=22.6 m/s and the...

Richard Feynman formulated quantum path integrals to show that a single photon can theoretically travel infinitely many different paths from one point to another. The shortest path, minimizing the Lagrangian, is the one most often traveled. But certainly other paths can be taken. Using single...

I am experimenting with using a radiometer as an approximate indicator of pressure in my homemade high vacuum system, running a small turbo pump. I am interested in the relationship between pressure and vane rotation speed, with light intensity being constant. I have only been able to find...

Is there any formula for underwater falling sphere which can measure the velocity of that sphere at any time before it reaches its terminal velocity? A sample question is: I dropped a sphere into water with 0m/s initial velocity. what will be the velocity of that sphere after 3s? {the radius and...

I’m just imagining spacetime that is spatially infinite but has a beginning in time. Naively, there would be only one (class of) reference frame(s with the same velocity) in which time starts simultaneously everywhere. (This is a naive application of “relativity of simultaneity” from SR.) But...

Problem Statement: I know that speed of light is 3000km per second Relevant Equations: Is it true? Can someone correct me if I 'm wrong,just interested thank-you

In vacuum and weightlessness, at the bottom of a cylindrical vessel (a cup), there is a layer of solid substance of molar mass μ. This substance sublimes slowly (evaporates from the solid phase into gaseous phase) and pushes thereby the vessel to the opposite direction. Estimate the terminal...

Hi, second problem in one evening, I'm sorry! But I'm also not quite sure if I did this one right. I had thought I need lenz's law but there is no current before entering the field so I just use the induced Voltage? My approach: ## V = \frac {B*A}{t} ## ## IR = \frac {B*A}{t} ## and ## A = v*t...

Dear all, I am back with another Spring problem. I have tried to use the insights I gained from your help last time: https://www.physicsforums.com/threads/find-v-x-of-a-mass-suspended-from-a-spring.972942/page-3#post-6190934 I figured I start with calculating the new equilibrium by ## x...

I am working on an Air Blast Cannon for work and am having trouble finding the proper formulas to calibrate it. This Cannon needs to have a barrel with about a 4 inch bore. It will only be used to generate high speed air blasts, so it will not have a projectile. Are there any formulas or online...

Hello to all good people of physics forums. I just wanted to ask, whether the angular and linear (orbital) speed in perihelion of eliptical orbit are related the same way as in circular orbit (v = rw). If we take a look at the angular momentum (in polar coordinates) of reduced body moving in...

Is there any device that can sort the particles of some medium according to the speed at which they move in the medium or something like that? As far as I know, there's a machine that can sort particles by charge through a magnetic field. Is there such a thing for speeds and charged / uncharged...

I have a proton and an electron at a certain distance from it. The proton exerts an electrostatic force on the electron. I then neutralize the proton's charge by firing another electron at it from behind. How long does it take for the first electron to sense the change?