Speed Definition and 1000 Threads

I have been having a conversation with a few friends, and we have been discussing the speed of stars in a galaxy base of the wave lengths. We have 2 stars measuring wave lengths 494.6nm and 494.2nm. At rest the wavelength is 486.1nm. From this we managed to deduce that the speed of both stars...

Hello. I read an article about aerodynamics. http://www.cyclist.co.uk/in-depth/2873/fat-v-skinny-who-goes-downhill-faster I'm a little bit confused with this statement regarding mass, drag, and velocity: "When you increase the mass the speed increases by cubic function, whereas if you...

For the critical speed of the shaft, should I include the weight of the members mounted on the shaft (gears, pulleys, etc.) with the forces acting on it?

Hello people, I have 3 questions related to the mean speed of electrons in a period potential /lattice. I've read Ashcroft and Mermin's page 139 as well as the Apendix E. From what I understood, if one applies the momentum operator on the wavefunction of a Bloch electron, one doesn't get a...

Homework Statement Determine sources of error which could have affected the results. Some background information: The lab consisted of playing a tone generated by a tone generator above a standing open-closed tube which had water in it. The first harmonic was measured through a computer system...

how do you describe the speed of an object in momentum space (energy, momentum as the 2 axes) where there is no distance or time? Can you give an example?

Let r = radius See picture. If r = 6 cm, R = 10 cm, and the angular speed of the larger wheel is 100 rpm, determine the angular speed of the smaller wheel in radians per minute. Again, 1 revolution = 2 pi radians. I need to use w = θ/t. So, θ = 100 rpm • 2 pi radians. θ = 200 pi...

I decided to change the radius. Let r = radius If r = 10 cm, R = 50 cm, and the angular speed of the larger wheel is 100 rpm, determine the angular speed of the smaller wheel in radians per minute. What are the steps to solve this question?

If you were to connect a string from one star to another (assuming everything remains still), and then you were to pull one side of the string towards you, the other would be pulled immediately, thus the "communication" between the two edges is technically faster than the speed of light? Does...

In circular motions, one can measure the NetForce on an object with this formula: ΣF = m*v^2/r. But is this formula valid even if the orbital speed of the object is constantly increasing (or constantly decreasing)?

Homework Statement Calculate the speed of sound in the classroom. You can use: Tuning forks, water, beaker, pvc pipe, ringstands, etc. Homework Equations v = f(wavelength) For fundamental frequency: L = 1/4(wavelength) For fundamental frequency: f = v/4L The Attempt at a Solution Here is...

Homework Statement I didn't quite understand my professor when he defined the speed of longitudinal wave. Lets say I have a slinky and on one side we act with a force F along the slinky. Well, he said that this part then starts to move with velocity v. But how? v isn't constant... Homework...

I have my students doing a lab where they have to do and explain the tablecloth trick using Newton’s Laws. The problem I am having is that the one question asks why the quick removal of the tablecloth matters. I know friction is not affected by speed and yet this is the only force acting on the...

The universe seems to be expanding since the farther away an object is, the faster it is moving. However, because of the finite speed of light, the farther away we look in distance, the further back in time we look. Does that mean that galaxies were moving faster in the past and are now slowing...

Hi there again, I have been wondering why train simulators(and trains themself) have a kW specification, AND a maximum force indication. If I would calculate the speed of a train using some formula, then where is the power value used for? Does it have something to do? Or is only the maximum...

Homework Statement A Higgs particle of mass M is moving in the z-direction with speed $\Beta_H$c compared to the lab system. It decays to a b-quark ans anti-b quark, each of mass m. What is the speed and direction of the b-quark compared to the lab-system, if the Higgs system, (a) it is emitted...

Hi there, So I asked a question here how I would calculate the air drag and the wheel drag of a train and I got an answer that made me very happy. Unfortunately i don't know where i could find the coefficient values required for the formulas. So i am wondering if someone knows where i can find...

Homework Statement Rank the rate at which the speed of each object is changing, greatest first. Ignore the sign; rank the magnitude or absolute value only. Homework Equations The red vector is the acceleration[/B] The Attempt at a Solution I have A>F>D>E=C and the program is telling me i am...

Hi, I am developing a Train Simulator kind of program where I calculate speed each frame. I currently do that by: Speed = (f/m)*elapsed frames*time between frames This works, but goes wrong when there are framerate drops or if the force changes, that's why i want to calculate the speed with the...

Hi there, I am new here so please don't be too hard on me yet and move this post if i placed it in the wrong forum. I am developing a little experiment game and i want the train to drive using real physics, but I am really bad at physics. So my question is is how do I calculate the friction of...

1. If A is static and B is moving away from A at velocity v, from Einsteinian point of view, is A also moving away from B at the same velocity? If yes, is the similarity of movements and velocities of both A and B valid in every context? If B is experiencing a time dilation from the view point...

Homework Statement A 0.5 Kg block slides from rest down an inclined plane as shown in the figure. The velocity at the bottom of the plane is 6 m/s. The vertical distance PO is 2m. (gravity = 10m/s2 If the block were to be dropped from P, what would be the velocity at O? Homework Equations K.E=...

Hello All, OK, I have been programming since the early 1980's. Programmed in many different languages along the way such as Pascal, C++, C, Visual Basic, and some C# (among others). I pretty much program so that I can model physics. I find it GREAT way to actually understand the physics...

Homework Statement A plane, diving with constant speed at an angle of 53 degrees with the vertical, releases a projectile an altitude of 730m. The projectile hits the ground 5.00s after release. A plane, diving with constant speed at an angle of 53 degrees with the vertical, releases a...

How does speed effect the recirculation zone and wake for supersonic and hypersonic speeds? Does it get longer, wider? Also this is for a blunt body like apollo reentering

If there was a positive curved time vs distance graph going upwards and to the right, would there be a speed for this graph even if all the points do not have a slope in common?

If I have a 7.5HP motor running at 1750rpm with a pulley and v-belt and connect it to a gearbox, where the right angle worm gearbox sees an input speed of 580rpm, how would I go about sizing the gearbox? Am I correct to say that I would size the gearbox for the lower input speed and more...

A particle without mass is supposed to travel at speed of light. But isn't it that a photon has no mass but has relativistic energy.. therefore why does it travel at speed of light.. or perhaps if a photon had no relativistic energy.. it would travel a bit faster than the current lightspeed?

How much pressure in PSI would it take to generate 150mph stream out of a 2 mm perfectly round orifice? And how many GPM would that equate to? Thanks for any help

Homework Statement In a report I am asked to assess the speed of response of various systems, however I am not exactly sure what this means, be great if someone could explain The Attempt at a Solution Step response plots were produced for each simulation and MATLAB was used to assign...

Homework Statement When a soccer ball is kicked toward a player and the player deflects the ball by "heading" it, the acceleration of the head during the collision can be significant. Figure 2-38 gives the measured acceleration a(t) of a soccer player's head for a bare head and a helmeted head...

10 seconds somewhere can be one on Earth due to time dilation, right? So In the case of distance wouldn't light have traveled more than 186,282 MPS since it had 10 seconds to travel relative to the 1 second on earth. So if light traveled at 186,282MPS for 10 seconds it would have traveled...

Homework Statement A satellite is in a circular orbit (radius R) around a planet of mass M. To change the satellite's orbit the engines fire and its speed is suddenly doubled. The engines fire for a very short time. Determine the length of the semi-major axis of the new orbit. Homework...

Homework Statement A train speeds past a pole in 15 seconds and a plate form 100 m long in 25 seconds. Its length is : Homework EquationsThe Attempt at a Solution x/15 = (x+100)/25 after solving this equation x= 150. but the ans is 180 m ? what should be the correct ans.

Homework Statement Hello, I havre problem here relevant to an image I will attach. ''A cricket ball hit by a batsman moves with a speed of 6m/s along a straight line path PQRS, as shown in the diagram. When the ball is at R, a fieldsman starts to run in a straight line from T with a speed of...

The question: If the max speed I can go in the universe is the speed of light measured from? Background: If there are three rocks in a vacuum along a line (the x axis), one is stationary (rock 1), one is moving 5 m/s in the x direction (rock 2) and one is move -5 m/s in the x...

Homework Statement If a spacecraft is traveling to a star which is located at a distance of 1 lightyear and it would take the spacecraft 1 year to reach the star in its own frame, how fast would the spacecraft actually fly? Also, how long would the journey take for an observer on Earth...

Hello everybody! For my water in nanoscaled-pores simulations with SPH I need a value for the characteristic velocity. My planned approach is to estimate this value by attaining the propagation speed of a diffusion wave. But I have problems with understanding this process since I find some...

I am having trouble understanding tangential speed as it applies to uniform circular motion and I would appreciate any help. Say I have a ball on the end of a string that I hold with my hand and rotate at a constant speed. If the string provides the centripetal force and acceleration, where...

Homework Statement 14.34 The 0.5-kg bob of the pendulum travels a complete circle about the pivot point O. Determine the smallest possible speed of the bob in position A if it is suspended from (a) a rigid rod of negligible mass; and (b) a string Homework EquationsThe Attempt at a Solution...

Homework Statement A current of 1600A exist in a rectangular (0.4 x 16 cm) bus bar. The electrons move at an average velocity of v. If the concentration of electrons is 1029 per cubic meter, and they are uniformly distributed, what is v? Knowns Current (i) = 1600A = 1600 x 1018 aA Charge per...

Homework Statement The speed of a runner increased during the first three seconds of a race. Her speed at half-second intervals is given in the table. Find lower and upper estimates for the distance that she traveled during these three seconds. It follows the image's square. Homework Equations...

This problem bothered me many years ago when I was taking a university course in quantum mechanics, but I assumed it was due to an error on my part which I, however, couldn’t locate, and I didn’t ask my course instructor about it. Recently, when researching a q.m. question on the Internet...

The two spaceships A and B approach each other at constant speed v: A----------B There is no way of knowing if B is standing still while A is moving at speed v (to the right), or if A is standing still while B is moving at speed -v (to the left). This shows that speed is relative. But if the...

In school, I was taught that the position of an electron relative to the nucleus is only an approximation. It is very likely that the electron will be close to the nucleus and where it is 'expected' to be, but it may in fact be anywhere in the universe. Is this correct? And does this allow...

So I followed the derivation of the Macroscopic Maxwell's equations by averaging the fields / equations and doing a taylor series to separate the induced charges and currents from the free ones. But why does light now "suddenly" travel slower in dielectric media? I mean, sure, it comes out from...

At supersonic speed, air become compressible. However why does Mach number decrease when flow area decrease? I understand that pressure will increase because the density will increase when flow area decrease. However shouldn't the Mach number increase in order to conserve mass flow? Unless the...

Sorry, me again. In another thread #47 I gave a experimental setup to detect an anisotropy in light speed of the form ##c(\hat{n}) = c_o + \alpha (\hat{n}\cdot\hat{v})##. It was pointed out quite correctly that the error incurred in the long arm to the sensor would cancel the anisotropy making...

Homework Statement I am having difficulty understanding the conversion between power and rotation at the engine and at the wheel. Can you please state which parts are right and wrong, and why please as I think I've spent that long on researching I've confused myself with too much information...

Has anyone encountered the term "hypersonic sound speed" in connection with fluctuations of thermodynamic quantities in condensed matter? How is hypersonic different than regular sound?