Speed Definition and 1000 Threads

I've having trouble understanding a derivation of the speed of sound waves, which is actually similar to another derivation I found a couple days ago. Let's suppose the sound is moving through water in a long cylindrical horizontal pipe. The premises of the derivation are 1.) For a given...

We know linear spring force F = kx(t), k = spring constant, during any moment t of energy release. displacement x(t) = ʃv(t)dt the power p = F*V = kx(t)v(t)= kv(t)* ʃv(t)dt My question: Is there a mathematical function of special v(t) to make power p constant?

Due to gravitational time dilation, the speed of light in outer space will be higher than on Earth. Do astronomers use the corrected value?

[Mentors' note: This question was orginally assumed a train traveling at the speed of light. Further discussion shows that this assumption is not required for the question; any relativistic velocity is enought to raise the question. The post has been edited, changes in boldface, to reflect...

Let us consider the co-moving observer ##\mathscr{C}## for whom ##E = \epsilon## and ##\mathbf{\vec{V}} = \mathbf{\vec{0}}##. Doing the perturbation stuff to the first of the relevant equations gives$$\partial_t \delta \epsilon + \boldsymbol{\nabla} \cdot ([\epsilon + p] \delta \mathbf{\vec{V}})...

I solved this problem easily using Newton's second law, but I had problems trying to use mechanical energy conservation to solve it. How I solved using Newton's second law: ##\text{(part of the rope that is on the left)}\, m_1=x\rho g,\, \text{(part of the rope that is on the right)}\...

I had heard that computer processors are reaching the speed of light. Is this true, and if it is how do we combat this cap?

I thought the answer was no. I.e. the traveler's proper time always passes more slowly than a stationary observer's clock regardless of the traveler's direction with respect to the observer. I was watching Brian Greene's NOVA episode on time, however, and, at 23:15, he has a demonstration...

In this part of the lab we pushed a block on a flat table and let it slide until it stopped. So it is decelerating with no force being applied to it while moving. In this case acceleration is negative. The only force acting on it is kinetic friction. Therefore I have come up with the following...

A company called SpinLaunch claims it can get something to 2200 m/s by spinning it up on a carbon fiber composite arm. I'm trying to figure out the limit of that approach. How fast can you go with existing materials? I tried to work it out for a constant with cable with no payload (result...

I need to calculate the overall uncertainty of the value I have obtained for the speed of sound in water, using Mackenzies equation... I am not sure in what way to combine the above uncertainties. Any help would be greatly appreciated! Lloyd

John is walking at a constant speed in front of a motion sensor. After 1 s, she is 2.5m from the sensor, 2 s later, she is 4 m from the sensor. a) Find an equation of in the form d=mt+b b) Determine the slope and d intercept and explain what they mean c) How far will John be from the sensor 5s...

It has been put to me that a simple spectroscope could in theory demonstrate the isotropy of the speed of light . By using a frequency standard (laser comb or Th Lamp for example) with the spectroscope in various orientations the lack of shift of the spectral lines would prove its isotropic via...

Chain length: 1400mm. Pitch of the chain:12,7 mm Diameter: Ø55 For z=12 Diameter: Ø71 For z=16 Diameter: Ø87 For z=20 Hello friends, Can someone who has knowledge of how to calculate the speed transferred to the sprocket wheel can help in such systems with various gear numbers (z = 20, 16)...

Let me clarify my question, is there any experiment directly proved the invariance of light speed to observers? Let's not get to the argument of equivalence between source and observer. SR was based on the postulate that the light speed is constant and independent of both the motions of source...

Yess! speed of light it's driving me crazy. I know it might sound too noob and silly but please enlighten me, First of all how does we concluded that speed of light is constant for every observer in all possible inertial frames of reference. Next thing how come a photon doesn't experience...

F= 9*10^9 (5*10^-9)^2 / (0.05)^2 a=F/m = F/(3*10^-6) v^2 = u^2 + 2aS = 0 + 2a*0.03 v = 60 Where did I do wrong? Thanks!

Is there a equation for the speed at the end of the whip. is there a consistent way to calculate how fast the tip of the whip will be including constant velocity and trajectory or is it chaotic. Im new to physics and had a thought that with enough legnth and power a wiphs end colud reach the...

1) Applying conservation of linear momentum: $$m.u = M.V + m.v$$ where ##V## is final linear speed of the rod $$V=\frac{m.u-m.v}{M}$$2) Applying formula of circular motion: $$V=\omega . r$$ $$\omega = \frac{\left(\frac{mu-mv}{M} \right)}{\frac{1}{2}L-x}$$ Is this correct?And can this be...

If charging some smaller toy, phone, electric razor, toothbrush or the like with induction charging I assume that the speed (time it takes to charge an empty battery) will depend on 1. the battery to some extent, but for this sake let's omit that 2. the inductive charging it self 3. wall socket...

The speed limits on a straight road are given by a known function g(x,t) where x is the location on the road and t is time. A car starts at x = 0 at time t= 0 and always drives at the speed limit. The location of the car is given by the (unknown) function s(t). Is there a differential...

The question is regarding an electrically excited synchronous generator. Consider that this generator is not connected to the grid and thus not locked with the grid frequency. This generator is spinning at variable speed and gets constant and similar excitation current meaning that the...

Velocity of photon allways is c(photon is massless particle).While velocity of EM wave in medium < c.So does velocity of photon need not allways equal velocity of EM wave?

a)Determine the slowest speed that the keys can swing and still maintain a circular path. Fnet = Fg + Ft Fc = Fg + Ft When Ft = 0, Fc = Fg So, Fc = mv^2 / r and Fg = mg mv^2/r = mg v = √gr v = √9.81 * 0.25 v = 1.56 m/s Therefore, the slowest speed that the keys can swing and still maintain...

Helicopter lift weight of 500kg ,weight is connect with load cell to meassure tension. Neglect aerodynamic drag.. If helicopter accelarate up ,tension is rope is greater than 500kg. If helicpter accelarate down ,tension is rope is less than 500kg. If helicopter fly up with constant speed...

Hi all, I need help understanding the light ray bending in the original GR 1916 paper, Die Grundlagen.... First of all, Einstein states the ##c## is not an invariant in GR. In fact, from (70) and (73), it stems that $$\gamma = \sqrt{ -\frac {g_{44}}{g_{22}} }, $$ where ##\gamma## is ##|c| <= 1##...

So clearly the easiest way to relate the angular speed to the linear speed would be to start from ##\tan(θ) = x/h## and take a time derivative of both sides. However, it also shouldn't be difficult to find the angular speed geometrically. Using the diagram below one can see that: ##sin(dθ) =...

Based on Maxwell equations, we can determine the speed of light as: $$c=\frac{1}{\sqrt{\epsilon_{0}\mu_{0}}}$$ Where ##\epsilon_{0}## is the electric permittivity of vacuum and ##\mu_{0}## is the magnetic permittivity of vacuum. This notation makes me believe that in other mediums those...

Light speed is impossible for anything with mass as more and more energy is required with increasing velocity. But this is only to an observer in a different reference frame. To the moving object, in its own reference frame, why would anything change regardless of how close to c it moves?

Hi, I have this question about the variation of wavelength and frequency as light travels to an environment with a different index. As we have learned in class, celerity can change as light enters a different environment, however frequency and wavelenght are independent and remain constant...

Suppose we're in a closed and non-expanding universe. You shine a beam of light in one direction such that it circumnavigates the universe and returns to its starting point from the other side. Now you put a detector at this starting point. Would this be a one way measurement of the speed of...

Attempted solution: Consider the instant when the normal force of the lower ball is zero. Conserving energy: $$\frac{mv^2}{2}+mgh_1=\frac{mv_1^2}{2}+\frac{mv_2^2}{2} + mgh_2$$ Applying the resulting torque to the upper ball where the rotation point is the lower ball. $$T=I.a =...

I have a 2-dimensionsal smooth function ##f(x,y,t)##. There may be multiple traveling waves across the domain. None of them are precisely traveling waves (the shape of the wave changes as it travels). Here is how one of these waves would look in 1-dimension: I want to find the speed of these...

I've been struggling with the problem below for some time. It is not a homework. A simple bubble S is a spherical surface that expands with constant speed c. A vector bubble V also expands with the same constant speed c. There is a 3d vector associated with a V. If two S bubbles touch, they...

PROBLEM: A 120 gallon tank (26" diameter, 60" height) containing 40 Gallons of water is heated up until the tank ruptures from overpressure at 125 PSI (maximum tank rating). How to calculate the initial escaped steam velocity at the ruptured tank, assuming the gash is 2 feet long in the...

Why do we know the velocity of all photons are the same as the velocity of light?Can we deduce this or we must have experiment test?What is the experiment test?

Hi. This is an idea which I just happened to think of, and I was curious if it would be at all feasible. Here's a quick sketch I drew: The two curved mirrors should have a laser attached on one end and a video camera attached on the other. The laser would be tilted very slightly above...

Does anyone know what the minimum speed of a gyro to make it so a force at 0deg will yield a movement at 90deg... or even better, what the angle is wrt speed... see http://www.copters.com/aero/gyro.html for pictures. -thx, rich

Hello Forum, The speed of efflux ##v_{efflux}## of a liquid, say water, from an orifice in the lower part of a container depends on the vertical distance between the free surface of the fluid and the lower position of the orifice in the container itself. The faster the speed ##v_{efflux}## the...

As in Bernard Schutz's A first course in general relativity, page 220, we suppose a gravitational wave travels in the z-direction with pure "+" polarization, so that the metric in the TT coordinate system is given by$$ds^2=-dt^2+[1+h_{+}(z-t)]dx^2+[1-h_{+}(t-z)]dy^2+dz^2 .$$ Suppose that two...

I have a Intel(R) Xeon(R) E-2274G CPU @ 4.00GHz 4.01 GHz machine which has a published max speed of 5.0 GHz. However, when I run it under load on all 4 cores, it only gets up to about 4.5 GHz: Could someone explain to me why it's not ramping up to the full 5.0 GHz or what I could do to...

Are the following statements true? --------------------------------------------------------------- If a speaker and a listener are stationary with respect to the air, a listener will measure the speed of sound at about 343 m/s. Since the speed of a sound wave in air is dependent only on the...

First calculated non conservative work from friction using Ff=umg. Non conservative work was -8.82. Initial kinetic energy, 1/2mv^2, was 136.89. Change in potential energy, 1/2k(x)^2, was 8.1216. Ekf-Eki+Change Ep=Work NC Ekf=W NC+Eki-change Ep =-8.82+136.89-8.1216=119.9484 Ekf=1/2mv^2...

its has been said that light slows down in glass, but some talk about phase velocity and group velocity... then there is the velocity of the photons, which some say is always c. What are those speeds [Vgroup, Vphase, Vphoton, Vlight] in glass, and what do they mean?

Hi everyone Could someone explain what happens in the body when metabolism speeds up? For example, does it produce more stomach acid? Or does it produce more concentrated stomach acid? Thanks

Starting from the microscopic form of Maxwell's equations and following standard mathematical procedure outlined in Inhomogeneous electromagnetic wave equation - Wikipedia we can have as end result the following equations: $$(\nabla^2-\frac{1}{c^2}\frac{\partial^2}{\partial...

So to cut to the chase, I missed my class' lesson on momentum - have tried to catch up, quite successfully but am baffled about this question. I know the conservation of momentum etc. but after trying for ages it's just not happening this question so any help would be much appreciated, Oscar.

Hi Pf I read that in the light propagator there are loops of electrons. What would be the consequences if we could switch them off (or neglect them)? would it modify the speed of the photons?

https://www.allaboutcircuits.com/textbook/alternating-current/chpt-14/circuits-and-the-speed-of-light/ Sorry, my other post must have been too brief. In another thread shut down by Dale, this very site (allaboutcircuits) was used by him to reference wave guides. This particular page is 100%...

https://www.allaboutcircuits.com/textbook/alternating-current/chpt-14/circuits-and-the-speed-of-light/Hmmmmm. :))