Speed Definition and 999 Threads

Let's say I can see a star in a distance of 1ly in front of me. I'm sitting on an office chair and begin to rotate with a speed of 1/s (1 rotation per second). Then I consider me as not rotating and everything else as rotating. Now I will see the star traveling a circular path with the...

Hey everyone I'm struggling on the last part of this assignment. I need to find the total work done by the block and the bullet, when the collision happens. The informations is: mblock=0.3 kg mbullet=0.01 kg vg=700 m/s Height=0.72m The final speed after the collision is vf=22.6 m/s and the...

Richard Feynman formulated quantum path integrals to show that a single photon can theoretically travel infinitely many different paths from one point to another. The shortest path, minimizing the Lagrangian, is the one most often traveled. But certainly other paths can be taken. Using single...

I am experimenting with using a radiometer as an approximate indicator of pressure in my homemade high vacuum system, running a small turbo pump. I am interested in the relationship between pressure and vane rotation speed, with light intensity being constant. I have only been able to find...

Is there any formula for underwater falling sphere which can measure the velocity of that sphere at any time before it reaches its terminal velocity? A sample question is: I dropped a sphere into water with 0m/s initial velocity. what will be the velocity of that sphere after 3s? {the radius and...

I’m just imagining spacetime that is spatially infinite but has a beginning in time. Naively, there would be only one (class of) reference frame(s with the same velocity) in which time starts simultaneously everywhere. (This is a naive application of “relativity of simultaneity” from SR.) But...

Problem Statement: I know that speed of light is 3000km per second Relevant Equations: Is it true? Can someone correct me if I 'm wrong,just interested thank-you

In vacuum and weightlessness, at the bottom of a cylindrical vessel (a cup), there is a layer of solid substance of molar mass μ. This substance sublimes slowly (evaporates from the solid phase into gaseous phase) and pushes thereby the vessel to the opposite direction. Estimate the terminal...

Hi, second problem in one evening, I'm sorry! But I'm also not quite sure if I did this one right. I had thought I need lenz's law but there is no current before entering the field so I just use the induced Voltage? My approach: ## V = \frac {B*A}{t} ## ## IR = \frac {B*A}{t} ## and ## A = v*t...

Dear all, I am back with another Spring problem. I have tried to use the insights I gained from your help last time: https://www.physicsforums.com/threads/find-v-x-of-a-mass-suspended-from-a-spring.972942/page-3#post-6190934 I figured I start with calculating the new equilibrium by ## x...

I am working on an Air Blast Cannon for work and am having trouble finding the proper formulas to calibrate it. This Cannon needs to have a barrel with about a 4 inch bore. It will only be used to generate high speed air blasts, so it will not have a projectile. Are there any formulas or online...

Hello to all good people of physics forums. I just wanted to ask, whether the angular and linear (orbital) speed in perihelion of eliptical orbit are related the same way as in circular orbit (v = rw). If we take a look at the angular momentum (in polar coordinates) of reduced body moving in...

Is there any device that can sort the particles of some medium according to the speed at which they move in the medium or something like that? As far as I know, there's a machine that can sort particles by charge through a magnetic field. Is there such a thing for speeds and charged / uncharged...

I have a proton and an electron at a certain distance from it. The proton exerts an electrostatic force on the electron. I then neutralize the proton's charge by firing another electron at it from behind. How long does it take for the first electron to sense the change?

I am stuck, please help. I did the conservation part but then i can't move on.

...Or even based on logic? I understand that it is expected that there might be a Universal Speed Limit and that this seems with extremely high probability to coincide with the speed of em transmission in a vacuum. This is borne out by experimentation and observation. Are there any other...

I'd like to know if anybody can tell me either; How large a wheel would have to be for the outer edge to travel faster than the speed of light if powered by a motor that's around now. We'll say the wheel is in outer space to eliminate drag and such

Hi, I am still working on the same exams problems, the second last one is giving me a bit of a headache after I found this https://physics.stackexchange.com/questions/2372/how-long-would-it-take-for-an-upright-rigid-body-to-fall-to-the-ground which contradicts my solution. Can I assume that when...

An electromagnetic wave has a phase speed and a group speed. Or velocities, for that matter. In a medium, the phase speed of a wave is generally determined by the medium's permeability μ and permittivity ε. What are the general parameters that determine the group speed of a wave in a medium?

Summary: how can a train traveling at light speed, travel at two different speeds being the same train, depending upon whether you are on the train platform or in the train You say good bye to your friend at the train station. You get into train that will travel at just under light speed...

Good afternoon everyone, I need help with a certain calculation. How much power is needed to pull a 250lb load up a 45 degree incline at 5 mph. I am working on a project at school and would like to know what kind of motor we can use. Thank you very much!

I have drone motor with propellers attached to the top of ring flywheels rim at the edge and the flywheel is 18 inches in diameter and weigh's 2kg. The drone motor with propellers rpm 5200 and thrust 900 grams. What rpm will the flywheel be rotating at.

During hurricane Lenny in 1999, I was anchored on my sailboat in a protected cove in the Virgin Islands. The winds were about 60 mph with gusts to an estimated 80 mph where we were. I observed that during the gusts, the salt water would "boil", that is, totally evaporate the surface into a cloud...

So using conservation of energy where v0 = 7000 m/s $$ K_{i} + U_{i} = K_{f} + U_{f} $$ $$\frac{1}{2}mv^{2}_{0} - \frac{GMm}{R} = \frac{1}{2}mv^{2} - \frac{GMm}{r}$$ where R = the radius of the Earth and r = the distance from Earth's center plus the height its orbiting $$v =...

(4+.9)(Wf)=(4+.63)(.27) (4.9)(Wf)=1.2501 Incorrect

I am wondering if an object can fall into a black hole at faster that the speed of light. I have heard that the expansion of the universe can make distant galaxies appear to recede from one another at velocities faster than the speed of light.

 Intuitively, this makes sense to me. I am...

I know this question has been asked before but I really need some help finishing this final piece of the puzzle.. I have attached an image of my work to show how far I have gotten towards the solution but my unfamiliarity with trigonometry equations has gotten my stuck. Please assist! thank you

I've tried using this equation: Where: u' = 0.86c v = 0.3c u = Is the speed of Q2 as measured by an observer in the reference frame of Q1 = 0.922c Where have I gone wrong? Have I missed a negative symbol?

I just recall the two expression for the Maxwell-Boltzmann distribution: $$ P(v)dv = \left( \dfrac{m}{2 \pi k T} \right)^{3/2} 4 \pi v^2 \exp \left(- \dfrac{mv^2}{kT} \right) dv \qquad P(E)dE = \left( \dfrac{4E}{\pi} \right)^{1/2} \dfrac{e^{-E/kT}}{\left( kT \right)^{3/2}} dE$$ The left...

Is it possible that time is just another coordinate axis? That it can be moved freely into backwards and forwards at any speed. And for some reason we as humans can only see it moving forward? and communicate at a definite speed in time. Maybe everything is already calculated and solved, and...

If my car can travel the speed of light will the head lights still work?

I have a question I have been wondering about lately ,somewhat abstract . Hopefully my description will be adequate . Here it is … The Earth revolves around the sun because of the suns gravitational pull and Earth's inertia . It takes about 8 minutes for sunlight to reach the Earth . What would...

1. How did one came to the constant 299 792 458 m/s? 2. Why this particular number? Why not 521 334 992? 3. Why can't we travel faster than the speed of light?

Problem Statement: The Doppler effect is routinely used to measure the speed of winds in storm systems. As the manager of a weather monitoring sta- tion in the Midwest, you are using a Doppler radar system that has a frequency of 625 MHz to bounce a radar pulse off of the raindrops in a...

mass of N2 = 28 * 1.67e-27 kg not sure if this is the right one - just googled it triple covalent bond N2 radii = 54e-12 m I tried to first find the rms speed: v = x/t = 50 * 54e-12 / 3 m/s Then I solved for T (in K): [50 * 54e-12 / 3]^2 * [28 * 1.67e-27] / [3 * 1.38e-23] = 9.14e-22 K

My first most obvious attempt was to use the relation ##<\epsilon> = \frac{3}{5}\epsilon_F## and the formula for kinetic energy, but this doesn't give the right answer and I'm frankly not sure why that's the case. My other idea was to use the Fermi statistic ##f(\epsilon)## which in this case...

I'm doing some exercises about special relativity and one of them asks to find the speed in an arbitrary frame of reference (1) in such a way that it perceives two events at the same time that didn't happen simultaneously in other frame of reference(2). Is it correct to state that if the...

Quantum entanglement does not imply that you can send information faster than the speed of light since you cannot manipulate what your sending. You don't know what you have until you have measured it. But you do know that you have the corresponding photon at the other location in space no matter...

Maximum Slip s=4/35 Synchronous Speed ns=50*60/p ns=3000 rev min-1 Speed at Maximum Torque Torque is maximum when R2=sX2 For maximum torque, X2=R2/s I'm not sure after this.

Hey everyone, I've watched some youtube videos on special and general relativity. A sentence that I heard over and over again puzzles me. "If I were in a closed space, there would be no way of distinguishing between acceleration and gravity." And there is supposed to be no way of telling how...

In a vacuum the speed of light is a constant. What if its not in a vacuum? Okay, as always I'm confused. I'm very interested in physics but am a layman. Alright, so we know that time is relative to one's distance from a mass, so that as we go further from the Earth, let's say, time moves...

Rod R1 has a rest length `1m and rod R2 has rest length 2m. R1 is moving towards right with velocity v and R2 is moving towards left with velocity v with respect to lab frame. If R2 has length 1m in rest frame of R1, then v/c is what? ----------------------- I let vel of R1 be u, of R2 be w...

For particle Q: The resultant force on particle Q would be zero since it is at rest. Thus$$ T - Mg = 0$$ which gives $$T = Mg$$ For particle P: This is where I am struggling. I can't seem to write out the polar equations of motion. I have to show that $$u^2 = (Mgb)/m$$ I know that $$\vec a =...

The second postulate says the speed of light is constant c independent of all inertial observers. Does it mean the speed of the wave front relative to the observer , that is, the relative speed between the wave front and the observer?

Field Current If=25-3 If=22 A Field Resistance Rf=250/22 Rf=11.36363636 Ohms Back EMF E=250-3x0.4 E=248.8 V New Speed New Speed = (Old speed)*(V-If*Ra))/E New Speed = (750)*(250-22*0.4)]/248.8 New Speed = 727.0900322 rpm Where can I find the appropriate formula for the change in speed in...

Hi! I'm currently doing a project to simulate a water slope, and want to find the maximum speed of a person going downhill in function of the water flow. At first I thought using a combination of the Manning equation and the Newton Law for viscosity, through the sheet of water, but I'm in a dead...

d² = 40² + 60² ---> I 60 = V.t ---> II 40 + d = V.(t + 1/8) ---> III Thanks in the advance. :)

I already got the answer for the case a but at the case b, i don't know how to sum all of the torques. I'm thinking of using integral, but i don't know where to put the pivot point for the torque. I don't know how to search for the pivot point. Can anybody give me hints so i could find the pivot...

To write ##v## as a function of time, I wrote the equation ##m\frac{dv}{dt} = c_{2}v^2 + c_{1}v - mg \implies \frac{mdv}{c_{2}v^2 + c_{1}v - mg} = dt## To solve this, I thought about partial fractions, but several factors of ##-c_{1} \pm \sqrt {c_{1}^2 +4c_{2}*mg}## would appear and they don't...