Speed Definition and 999 Threads

It appears that the most probable energy level according to the Maxwell-Boltzmann distribution is not equal to the most probable speed squared multiplied by ##\frac{1}{2}m##. The most probable speed has a different value. $$E_{max} = \frac{k_BT}{2}$$ $$v_{max} = \sqrt{\frac{2k_BT}{m}}$$ I am...

Hi PF! I'd like to test how fast my cpu clock speed is. Any recommendations with benchmarks so I can see just where I fit?

As much as i search Google, in an effort to find out how exactly the constancy of speed of light was historically deduced before 1905, from Maxwell equations or by any other means, i am not able to find such an explanation. In all of the search results that i could find, it is just stated that...

I have successfully composted before,(for planting) but is there a way to speed it up, maybe with mycorrhizal? (I hope this is the right section) I live in a hot (35C-48 C or 95F-120F) dry environment and I know to keep it damp (not Dripping) and well mixed (add air)

Here is the Q Very unsure about how to approach this question but this is what I have tried Any help would be really appreciated! Thanks

I've always thought that light could possibly be transmitted faster in one direction than the other depending on the velocity of its container - despite what the current understanding of physics says! The problem is that its very hard to prove, and to this end I've read through all the...

Hi, I read various threads in PF about the concept of invariant speed and the speed of light in vacuum that in our universe happens to be the same as the 'invariant speed'. My doubt is about the speed of the light in vacuum as measured from a non-inertial frame (basically in the context of SR...

I recognise that the normal force must alwayss act towards the centre of the circle loop, as the rail always has to be exertign a pushing force on the car/carriage in order for it to follow the trajectoryof the loop. However , I cannot understand why, the reaction force has to be greater than...

Which one does it mean: "phase velocity" or "group velocity" or "speed of the wave front"? In the postulate of constant speed of light .

Apparently, right now the Earth is spinning at 1,000 mph! From https://www.space.com/33527-how-fast-is-earth-moving.html "Earth's spin is constant, but the speed depends on what latitude you are located at. Here's an example. The circumference (distance around the largest part of the Earth) is...

Hello, I consider to be in a relativistic area, where an object is moving very fast, seen from our Earth, at a speed v where v is less than the speed of light c. I have considered the following equations (relativity equations) : T = β * t M = β * m L = l / β β = 1 / (√(1 – v2/c2) )...

What is the equation/formula for the Speed Of Light? E=mc²? I thought it would be simple to find in a search.

Hello everyone! Let's say that you were to attempt to go as fast as possible on a spaceship with the mass of an average car in an absolute perfect vacuum. What I am wondering is, that if you were to reach a certain speed, and stop applying energy to this imagined spaceship, would the spaceship...

I get two different answers even the area of the graph. I think there is something wrong with the equation I constructed for average speed part. I know the method 1 is correct. But I'd like to know why the average speed cannot be used. And why I get two different areas for the graph Thank you

Is it technologically feasible today or in the near future, to accelerate in outer space a ~0.1 gram physics experiment lab, inside a cyclic accelerator and shoot it in a straight line at a constant speed of 5%-80% of the speed of light? That miniature capsule, must include all that is needed...

Isn't the meaning of speed, a variable of distance divided by a variable of time? Therefor isn't the meaning of a constant speed of light, a constant distance divided by a constant time? If there is any truth in this saying and there probably isn't, then what is the meaning of light constant...

If i am moving away from an object at a certain constant speed close to the speed of light, is that object also moving away from me at the same constant speed?

Would it be correct to say, that we are moving away from stars at the edge of the universe, at the same rate that these stars are moving away from us? I am relating to stars that are moving in relation to us, at a speed that is faster than the speed of light. Is the symmetry that maintains that...

To describe the movement of the planets, Newton assumed that there was such a thing as gravity. But he didn't know what gravity was. To derive the Lorentz transformation, Einstein assumed that the speed of light was absolute (not relative), but is it also known why the speed of light is absolute?

Hi! I just watched a video about cardio training, where it is claimed that the only thing that matters is the distance covered, and not the speed. "Four miles burns more calories than three miles." So, walking four miles burns more calories than sprinting three miles. (Click the link and watch...

I ran into something on a non-technical message board that is familiar to me - a poster, clearly without any scientific knowledge, saying that Relativity is wrong. Unfortunately, the point he used as a battering ram is one to which I don't know the answer. He suggested that the light...

I understand that the meter is defined from the speed of light (distance light travels in 1/299792458 of a second). But how did man measure this exact distance to this level of precision? With any apparatus, isn't there an unknown amount of bottleneck somewhere?

If route perpendicullar forces supose to have no affect, why isn't this the case when somebody tries to cross a river? the motion is perpendicullar when water speeds aprox. at the same direction.. what am i missing?

I first found the height of the ball after it's passed the 45 degree angle by doing 4.12*sin(45) = 2.9133, and plugged in the rest of the variables (masses cancel) .5(m)(vo^2) = (.5)(m)(vf^2) + mgh (17.5^2)(.5) = (.5)(vf^2)(9.8*2.9133) vf = 15.7845, however this is incorrect I don't understand...

Frequency nU = W/2pi = 287.6/6.28 = 45.796 = 45.80 Speed C = nU * I = 45.80 * 186.9 = 8560 m/s

Fgravity = m*g Ffriction = k*A*v^2 Ftotal = Fgravity - Ffriction a = Ftotal/m v = v+a*dt if t<7 then Fgravity>Ffriction if 7<t<67 then v =55,88 (meters per second) if t>67 then A = 45 (square meter) if t>67 then Fgravity<Ffriction the t defines the seconds the first 7 seconds are the free fall...

If we assume the energy of particles in an ideal gas follows a Boltzmann distribution, then the energy distribution function can be defined as below: , where k_B is the Boltzmann constant Since the energy of particles in an ideal gas are assumed to only consist of translational kinetic energy...

Is there any reason to believe that the one way speed of light is constant? Not isotropic, but constant in the sense of being independent of position.

I had many attempts on trying to solve this one, but I got always stuck in the problem-solving part: how do I manage to find the source-speed from the Doppler formula, in an analytical way, and then reach to the result-formula? Anyway, I'm pretty sure the only formula needed to solve this...

Someone asked me what a dime was (this is UK.) I, not knowing, nevertheless promptly replied, it must be 5 cents, because they called their 55mph speed limit the double dime. Then of course went to Google to check and found that it is 10 cents. How does double 10 become 55? So back to Google...

Moderator's note: This thread is a spin-off of https://www.physicsforums.com/threads/what-are-the-most-important-open-questions-in-classical-physics.983671/ R. de Sangro, G. Finocchiaro, P. Patteri, M. Piccolo, G. Pizzella, "Measuring propagation speed of Coulomb fields", Eur. Phys. J. C 75...

First of all I thought it was necessary to calculate the temperature(the only data missing for the formula) using the ideal gas equation(since I've already been given 'p' and 'V'), and plug it in the 'v' formula, but the problem immediately occurred when i tried to find out the number of...

In the picture, there is a problem where the t is in units of square root(l/g), and V in square root(gl) I am wondering 1. What it means when time is in units other than time? Does it mean that when solving I have to take time/squareroot(l/g) 2. How did they get square root(l/g). Thank you...

Hi,i want to calculate the speed of sound in water Containing Chlorine : 4mg/L in 1L distill Water Chloroamine : 4mg/L in 1L distill Water Florides : 0.5mg/L + in 1L distill Water Copper : 0.005mg/L + in 1L distill Water Lead : 1.3 mg/L in 1L distill Water Can you please help in...

I am confused why the acceleration doesn't point to the center of the ellipse or one of the focus, since it moves in circular motion. Shouldn't the acceleration be just in the radial direction

Hello, I am trying to solve a problem at work that at first I thought was easy but has proven trickier than I originally thought: If I have a strip of material traveling in a straight line and it is tangent to a roll turning below it, the roll would need to turn at the surface speed of the...

I have a "262 Lionel Line" O gauge train, from the early 1930's. It has sentimental value, my Father-In-Law (RIP) got it as a gift when he was about age 10. I've set it up each Christmas, a short track around the tree. But it is difficult to control, the gearing is high (it goes fast), so...

Hello all, I am an engineer with a manufacturing company and I am working for calculating the critical speed for a vertical cantilever slurry pump. This pump design includes one ball bearing and one taper roller bearing within the bearing housing. Then the shaft extends vertically downward...

I take the following example to explain my question : when a « black-hole » is attracting a planet there is a Force which is proportional to the 2 masses and inversely proportional to the distance between the 2 masses. When the planet moves towards the « black-hole » this attraction force...

My solution is very sketchy, but we want the math right. However, I've came to 2 thoughts that helped me get to the solution, and those are: The only way that you can launch a ball at a velocity and have it be the same velocity two seconds later, is if it's already reached its maximum height...

I had the wonder of whether, due to the speed difference, clocks ran at a different speed on the equator than on the poles. I then researched this, and found that, due to being closer to the centre of the Earth at the poles due to the bulging of the Earth due to spinning, the two essentially...

This means the sound wave reaches the outlet faster as it travels in the same direction as the medium. But I was reading online that speed of sound is independent of the medium so I don't know why my professor used this approach. If speed of sound was dependent on the medium, then wouldn't shock...

According to the 2nd postulate of Special Relativity, speed of light in vacuum is the same in all inertial reference frames. If I take a beam of photons and see the other photons in the beam from a frame of reference of a single photon, do they look stationary or moving at the speed of light...

I have a speed estimator that calculates a cyclist's Steady State Velocity v given the rider's power output p (watts), rider mass m (kg) and hill gradient g. For this particular model, headwind and tailwind beyond the drag force conditions are not relevant. In the model I use, there are three...

When we say speed of light = c m/s. Who is measuring meters and second. From SR perspective, that photon is moving towards you at speed of light so there should be time dilation, correct?

Car A hits Car B's passenger side at intersection (T Bone). Car B flips over sideways in the direction of the driver's side. The intersection is basically level. Car A is an Audi 5, roughly 3,900 lbs. Car B is a Lexus NX, roughly 4,000 lbs. Car B had recently stopped and was traveling...

The speed of sound in a gas at temperature T is given to be ## v=\sqrt{\frac{\gamma RT}{M}}##, where ##\gamma## is the adiabatic exponent, R is the gas constant and M is the molar mass of the gas. In deriving this expression, we assumed that the compression and expansion processes were so fast...

Summary: Can the speed of information be faster than light? Say you had two people in space and they were 10 light years apart. Each person has a light bulb and battery connected to an electrical switch. Pressing the switch turns the light on, once it is released it springs back to the off...

Recently, I've been studying about Lorentz boosts and found out that two perpendicular Lorentz boosts equal to a rotation after a boost. Below is an example matrix multiplication of this happening: $$ \left( \begin{array}{cccc} \frac{2}{\sqrt{3}} & 0 & -\frac{1}{\sqrt{3}} & 0 \\ 0 & 1 & 0 & 0...

I am reading up on the special theory of relativity, and watched a video. In the video we have a train moving at ½ c towards a station, where an observer is waiting. The train's headlamp is on. How would the lamp's light appear to the observer? I was thinking that it¨'d appear to the observer...