Speed Definition and 1000 Threads

Do all humans have the same visual processing speed or does it differ from person to person? By ‘visual processing speed’, I mean the speed at which one takes to process visual information. For example, if a light has a frequency of 50 hertz where it switches on / off 50 times a second, do all...

A thought experiment about the speed of light. Say I build a 600,000 km long tube around the circumference of the Earth at the Equator. The tube's inner diameter is constant at 54.4505 mm. A snooker ball is perfectly manufactured to its lowest tolerance by a special new machine. Each one is...

Hello, Nice easy question for you all today: I would like to know how the speed of sound in steel varies with temperature. A google search didnt reveal a great deal, so if a physicist could confirm the relationship, that would be much appreciated. I know that: v = √shear modulus/density...

It seems that with the 2016 LIGO and VIRGO confirmation of the gravitational chirp that we have also experimental confirmation that the speed is indeed the speed of light. True? https://en.wikipedia.org/wiki/First_observation_of_gravitational_waves#Direct_observation

Homework Statement Suppose that a heated gas comprised of electrons glows bright orange when it is in use. Estimate the average speed of the electrons in the gas. Model this gas as an ideal gas. Homework Equations None. I have no clue. This is a "review" question on a chapter titled "Current...

When I read the speed of light in vacuum is c, does it imply that light doesn't actually travel at this speed in nature? My guess is no, light always travels at c, it's just that in the definition, we're trying to ignore the affects on light from other stuff like the comological constant and the...

http://imgur.com/a/hFubT http://imgur.com/a/fquuF In the first image, first line in the last paragraph. The first sentence define that carriers move with an average velocity component Vd in the x direction(in fact, carriers also move with an average velocity component in the y...

Hey people, I just want to ask that what will happen to the total mechanical force of the rocket if its speed is less than escape velocity? a. KE+PE=0 b. KE+PE>0 c. KE+PE<0 d. Depends upon initial speed of the rocket Pick one. And Why??

Homework Statement If you walk to school at 4 mph and jog home at 6mph, what was your average speed? Homework Equations S = D/T The Attempt at a Solution Is the average speed not just (4 + 6)/2 = 5mph ? If not, why not?

Wouldn't the first thought be that we would be burned to a crisp if we where hit with all the light(in our path) across the span of the entire universe simultaneously? It seems there could be paradoxes even before the advent of relativity. Or maybe it was shown mathematically that the energy...

Sorry if the title was a little vague, character limits. The question at hand is this; If you were to accelerate an object to near speed of light, time around it would speed up, thus forward time travel. We all know this and I am no expert in this area but am incredibly curious. (Assuming we can...

Homework Statement Discuss how Newton’s Laws can be used to explain the introduction of transportation safety features such as: Speed Limits on curved ramps Homework Equations Newton's 2nd Law: F=ma The Attempt at a Solution I believe that according to Newton's first law objects that are in...

Homework Statement Given the Speed of vehicle at any instant (say 30 meters/s) and Heading of a vehicle (say 270 degrees ) , how can i find the velocity components which is Vx and Vy . Lemme tell you about the Heading ...This is the convention.. I don;t know if this pic is viewable or...

Hi everyone, I remember years ago at school memorising the derivation of the formula for pressure in the kinetic theory of gases, as explained in this Youtube video: Thinking a little more deeply about this derivation there are two things I don't get: 1) At 0:53, the video says the molecule...

Can someone point me to a resource that describes, or describe, how the orbital speed of stars within galaxies are observed and measured? I'm struggling with how these values can be attained with any confidence in their accuracy. Thanks :)

Homework Statement There are two cars traveling in a same direction. The Second car has a camera mounted on it and has ability to give relative X and Y (in meters) distance of first car with respect to it. Given the Speed of Second car , Calculate the Speed and Acceleration of first car. The...

Okay...I read that speed of a wave for a particular medium is constant, i.e it is independent of its frequency and wavelength...Hence we can conclude for a particular medium, all waves travel with same speed...Is' nt it contradictory with our usual observed phoenomenon..Like, if we take air for...

I'm wondering how does speedometer work. To be specific let's talk about car speedometer. I googled it and found out that there are different kind of speedometers, but not quite understood it's working principle. My question is not about how it shows us speed (Mechanically with arrow or...

It is said that due to the expansion of the universe, there are some distant galaxies that are moving away from us faster than the speed of light. They can't actually move faster than speed of light itself, because the law of physics over there are supposed to be the same as the law of physics...

The speed of light is postulated to be constant in all inertial frames. but why is it called a postulate actually? looking at the SI definition of the meter that is specifically defined by the propagation of light i notice it makes it constant by definition. so isn't this actually just a choice...

Homework Statement A solid sphere of radius 16cm and mass 10kg starts from rest and rolls without slipping a distance of 9m down a house roof that is inclined at 43 degrees. What is the angular speed about its center as it leaves the house roof? The height of the outside wall of the house is...

I was watching a seminar on black holes and one of the participants threw out as an aside that spacetime could travel faster than the speed of light - so within spacetime nothing could travel faster than spacetime but spacetime itself however was not bound by this rule so it could move faster...

ship A is traveling at 30 km hr^-1 in a direction 60 degrees E of N. Ship B is 20 km east of ship A traveling at a constant speed. find the minimum speed of ship B to intercept to intercept ship A i know there distance in the j direction must be the same but when i let 30cos60=xsiny it does...

If you were in a warp drive spaceship traveling at say 2c. Would all observers see your ship traveling at 2c?

This may be an odd question but I am wondering if water speed affects a bullet's ability to penetrate water. Pardon my lack of knowledge, but I am aware that low caliber bullets can penetrate water past 3ft (Thank you Mythbusters). However, the tests they completed were all based around a pool...

Hi All, I have a VFD running supply fans and I currently have two values I can see. One is the VFD actual speed percentage from the VFD. The other is a calculated Fan Speed based off of VFD current. (I control off the calculation). The calculation is (Current^.33)*25.54=%. Does anyone know this...

Can the magnitudes of speed and velocity be different for the same given situation?

I'm having no problem finding the maximum speed of a pendulum but I'm not sure when I move its start point and measure point. I would like to know the speed of a pendulum at 30 degrees that has been dropped at 140 Degrees. I'm just giving some numbers to explain that it is above the horizontal...

Homework Statement [/B] A wheel, of radius 200mm, rolls over the top of a hill with a speed of 20m/s and negligible friction losses. (I = 1/2mr^2) Homework Equations [/B] Find the speed of the wheel when it is 10m below the top. The Attempt at a Solution [/B] mgh = 1/2mv^2 + 1/2IW^2 W=...

Hi, I don't have any background in physics at all (perhaps besides knowing about the relationship between speed, distance and time). Rather I am considering making some video game about jousting, and I'm considering whether a physics based approach would be good for the user experience...

How did Einstein first contemplate the idea that the speed of light was constant in all frames or reference? Did he say "I wonder what would happen if we considered light speed to be constant" in some kind of thought experiment. Did the concept fall serendipitously from the results of...

Sound is vibration of air molecules knocking into each other. Intuitively, it seems the faster a molecule travels before hitting another, the faster the propagation of sound. Can't you hit air molecules harder, so the air molecules will travel faster and spend less time between collisions, and...

Homework Statement So, we have a ring 'A' having mass 'm' that can slide on the horizontal rod. It is attached to a massless string, whose other end is attached to a block of mass 'M = 2m'. 'B' is a massless and frictionless pulley. The problem states that at an instant, the string between...

Homework Statement Calculate the Belt pull, drum torque, motor power and speed required to drive a flat top belt given the following information: Belt centres are 4.0m Required speed is 18m/min Drum diameter is 300mm Belt mass is 3.0kg/m Belt is fully loaded with 32kg boxes 0.8m long Belt...

The speed of light (in the vacuum) is a function of the permeability and permittivity of the vacuum. In other mediums the phase velocity will be different. It is assumed (by me) that the speed of a gravitational wave does not change depending on the medium i.e. a gravitational wave would not...

From LIGO website re how gravity waves are measured: "The arrival times change because when the arms of the interferometer change lengths, so too do the distances the light waves travel before exiting the interferometer. What gravitational waves do not change, however, is the speed of light...

Hi, I've built a coilgun using a solenoid, but my projectile stops at the half of the road, but this way i can't measure neither the acceleration nor the speed. what could be wrong ? how to push it further ? I also have a question about the efficient methods to measure the speed of the...

This may be a rather ridiculous inquiry, but Google queries haven't helped much. As I understand it, different colors (wavelengths) of light move at the same speed in a vacuum, which together make up what is often called "white light." However, when light enters the Earth's atmosphere, its...

Homework Statement Fast electrons in synchrotron approach the speed of light: I don't get to the "one part in 8,000,000" Homework Equations Momentum: ##~P=mv=\frac{m_0v}{\sqrt{1-v^2/c^2}}## The Attempt at a Solution...

[Moderator's note: this was originally the second part of a post in another thread; it has been moved to this separate thread.] PLEASE BE ADVISED: I'm a complete ignorant with regards to the details of what I'm about to say and I've never looked at the mathematics of the subject, let alone...

Speed of a wave in a string is given by √(τ/μ) . But this speed is with respect to which reference frame? Since, the speed depends on τ and μ( which are independent of reference frame ), I can consider speed of wave independent of reference frame. But this is not so. From experiment, we know...

Hi guys I'm finishing up some promo art for my original comic book. You're seein it here first. But its missing something- an appropriate equation. I would like to integrate a math equation into the art. I am attempting to depict FTL travel, using qualities similar to an LWFA, the plasma being...

Homework Statement Starting from rest an airplane lifts off the ground after 40s and 1.8km. What is its speed at takeoff and its average acceleration during the takeoff run? Homework Equations V= distance/time Acceleration= (Vf-Vi)/time The Attempt at a Solution The airplane travels 1.8km in...

Homework Statement Homework Equations 1/2 mv^2 E = hf c = f (wavelength) The Attempt at a Solution 0.5 * (9.109 * 10^-31) * (6 * 10^4)^2 = energy energy = hf => f = energy/(6.626*10^-34) = 2.47 * 10^12 wavelength (m) = (speed of light) / frequency wavelength (m) * (1*10^9) = 121235.4 Answer...

I think I understand the relationship between the three, but I would like some feedback. I still am fairly unsure about lens speed and is what I'm mostly interested in. From my understanding: Aperture is the total diameter of the lens and numerical aperture is the ratio between the aperture and...

I am aware that an observer in free fall in a gravitational well will measure the local speed of light as c, but what about someone outside the well. Imagine this, Me and my friend are near Earth, and he starts freefalling to the surface, while i stay in space. If he then fires a laser beam at...

Just recently I came up with a new idea to measure one way speed of light and/or synchronize distant clocks: Let’s have two light sources at points A and B separated by distance d and sending constantly (perpendicular to AB) signals to clocks at A’ and B’ Let’s have an opaque rod of the length...

In the wave equation## \frac {\partial^2 \psi} {\partial x^2}=\frac{1}{v^2}\frac{\partial^2 \psi}{\partial t^2}\tag{1}##, v is the speed of the wave propagation. With respect to which reference frame is this speed measured( in general)?

Homework Statement an asteroid heading towards earth, has a speed of 7.25 km/s as it passes the moons orbit, kit misses Earth by 5000km. What is the speed at the closest point to earth? The professor provided us with the solution, which should be 11.0 km/s, however when I do the calculation...

Okay...The speed of light is affected by density of the medium in which it propagates...It is more in rarer medium and lesser in denser medium...Hence we can conclude that a medium affects the speed of light...My question is that why this ''affect'' is not ''continuous'', like why the speed of...