Speed Definition and 999 Threads

Homework Statement Homework EquationsThe Attempt at a Solution I have solved the first part already. For the 2nd part, I am writing the relevant eqns. Can I take motion of the plank as a pure rotation about the pivot ? Quantities corresponding to pivot is subscripted by p. Conservation of...

Homework Statement Homework EquationsThe Attempt at a Solution In rolling motion, friction doesn't work. So, applying work energy theorem, ## \frac 1 2 m v_0 ^2 =\frac 1 2 mv^2 + \frac 1 2 I_{center} \omega ^2 ## ## taking~ I_{ center} = \frac 2 5 m R^2 ~and ~ v =\omega R , v = \sqrt {(...

Homework Statement Homework Equations Angular momentum = moment of inertia * angular velocity Change in angular momentum = impulsive moment v^2=u^2+2as The Attempt at a Solution First I used v^2=u^2+2as to find the velocity of the particle the moment the string goes taut. I got v=\sqrt{8ag}...

Homework Statement Homework EquationsThe Attempt at a Solution A) Assuming no gravity The only external force acting on the mass m is tension and the torque due to it about the axis of post is 0. Hence, applying conservation of angular momentum about the axis of post gives, ## m v_0 r = m v...

Relative to the observer, objects shorten when approaching the speed of light exponentially. Does this rule also apply to the wave function? Does this rule also apply to massless particles like Photons? Or am I just simply forgetting something?

What determines the speed of a sensor (keyboard and cameras) transmitting data from the external world (pictures, sound) into the processor (CPU)?

Hi Please have a look on the attachment. Do you also agree that the shell strikes the water at the same speed? It seems false to me. The vertical and horizontal motion is independent of each other. When the shell is fired horizontally, it starts descending toward the ground from less height...

Homework Statement Using a radar gun, you emit radar waves at a frequency of 2.6 GHz that bounce off of a moving tennis ball and recombine with the original waves. This produces a beat frequency of 730 Hz. How fast was the tennis ball moving? Homework Equations fbeat = fa - fb v=λf f=1/TThe...

Homework Statement A billiard ball moves at a speed of 4.00 m/s and collides ELASTICALLY with an identical stationary ball. As a result, the stationary ball flies away at a speed of 1.69 m/s. Determine a. the final speed and direction of the incoming ball after the collision b. the direction...

SOLVED THANK YOU

I have as advised done some catching up on basic cosmology, looking at various discussion and lectures on the nature of the universe. Something that has always played on my mind, is that i remember reading and watching a documentary about the potential to achieve the velocity of light. It was...

Homework Statement Mod note: Fixed thread title. OOPS NOT Acceleration, Speed! (Thread title is incorrect) Homework Equations w=d∅/dt v=rw x={+,-√(b2-4ac)}/2aThe Attempt at a Solution I solved this with help from Chegg study, however, I'm still not entirely sure what I am doing. Obviously, for...

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...