Speed Definition and 1000 Threads

  1. S

    Engineering Calculate consumption, displacement and speed using given standards

    I calculated the value of kgf/cm^2 from given values. In the second table (Force exerted by the pneumatic cylinders) I see my value 5.6 exactly but how do I then read the table to get the diameter of the cylinder and then the rod? I then am stuck on how to calculate the total consumption...
  2. A

    The Nuclear Rocket that Could Reach 20% of the Speed of Light

    In 2009, the same society together with the Tau Zero Foundation announced Project Icarus, a similar spacecraft that could achieve 15% the speed of light. That year, a physicist called Friedwardt Winterberg announced a fusion spacecraft that could be used as a capacitor to produce proton...
  3. A

    Angular speed, acceleration, and angle of a Ferris wheel

    ω(10)=(1.3)∗(1.0−e^(−10/22) )= 0.475 rad/s 0.475 rad/s=0 +α(10second) α=0.0475 rad/s^2 ∫ω(t)=Θ =1.3t + 28.6e^(-t/22) | (t=10s, t=0) total angle by which the wheel rotates over this period of t=10 seconds = 2.55 rad Θ= 2(pi)(8m)= 1.3t + 28.6e^(-t/22) 0=1.3t + 28.6e^(-t/22) - 2(pi)(8m) t=34...
  4. posto002

    With what speed does the cart recoil?

    I started off with vf^2=vi^2+2ad and plugged in the final velocity, acceleration (9.8) and distance which is 2.1 to get: 0=vi^2+2(9.8)(2.1) I solved this to get: vi=6.42 I then plugged this into find the x-component of vi (I labeled this as simply x)...
  5. J

    B Red-Shifted Light: Speed Less Than C?

    The wavelength of light from a moving source is red shifted which means that the wavelength has increased and the quantity of energy arriving per second at a relatively static destination is less than the quantity of energy emitted per second at the source. If so then the original quantity of...
  6. U

    B Train traveling near light speed

    A train is traveling around the Earth at just under light speed. Light would circle the Earth around 7 times per second so let's say this train cricles the Earth 6 times per second. There is a physical ticker on the track of the train that records revolutions. Each time the train makes one...
  7. Haorong Wu

    The speed of a spaceship flying through dust

    The given solution is: However, I could not agree this solution, and my solotion is: So which one is correct? it seems a exponential decay would be more convincing. Thanks!
  8. NoctusPartem

    How can I calculate the smallest speed of a proton in a nucleus?

    My approach: Assuming non-relativistic velocity: $$p = mv$$ $$mvL = \frac{\bar{h}}{2}$$ $$v = \frac{\bar{h}}{2mL} = \frac{h}{4\pi mL}$$ $$v = (6.626*10^-34) / (4pi * 1.67*10^-27 * 4.3*10^-15)$$ $$v = 7.34*10^6 = .0245c$$ This answer is incorrect. What have I done wrong? --- Edit: My...
  9. matternat968

    B Relative Nature of Speed: Einstein and Orbits

    At the risk of sounding stupid, this question has always perplexed me. Einstein theorized that mass can not travel faster than the speed of light. I don't really understand it, I assume it has something to do with mass just being energy. Anyway imagine two objects in orbit of something with...
  10. Frigus

    How can the pressure be more in liquid flowing with less speed?

    Before I have read Bernoulli's theorem I believed that pressure is more in liquid flowing with more speed but today I have read Bernoulli's theorem where this theorem says that the pressure is more in liquid flowing with lesser velocity please tell me how can this explained,with equation I...
  11. jk22

    I Photon Speed Addition: Can it Be FTL?

    It is well known that relativistic speed addition is a non-commutative group (gyrogroup). The addition of two orthogonal speeds is given by : ##\vec{u}\oplus_\perp\vec{v}=\vec{u}+\sqrt{1-u^2/c^2}\vec{v}## Hence if ##u## is describing a photon with speed c then we can add whatever ##v## it...
  12. EEristavi

    Water Pressure and 2 dimensional motion

    $$ H = \frac { V^2 - V_0^2 sin \Theta} {-2g} $$ $$ H = \frac {V_0^2 sin \Theta} {2g} $$ So, I need to calculate ## V_0 ## I'm thinking about pressure. $$ P = \rho g \Delta h $$ $$ \Delta h = h - L sin \Theta $$ $$ F_A = P S_A $$ $$ F_A = P S_B $$ Dead End here...
  13. J

    I Speed of Light Paradox: Neutron Star Rotation Rate

    Sorry if this is a stupid question but I couldn't find an answer anywhere. According to 2 scientific papers, the neutron star PSR J1748-2446ad has a rotation rate of 716Hz, which equates to a linear surface speed of 0.24c. What if this star was originally rotating, let's say, 5 times (or more)...
  14. A

    Current: the speed of charges vs the number of charges past a point

    Current is determined as the amount of charge moving past a certain point of reference (like the point in a wire with current meter clamps around it) in 1 second. This got me thinking , so in a classical resistive load situation with Ohm's law there would be two ways to increase the amount of...
  15. G

    How is the speed of light derived in Maxwell's equations?

    I know we end up with ##c=\sqrt{\frac{1}{μ _0.ε _0}}## The reason I would like a bit of help is that I understand that the value of c as deduced from Maxwell's equations is independent of any frame of reference. I can see that this is the case from the above equation involving the...
  16. ColdheartedGod

    Why does the speed of light change in different media?

    In relativity, the speed of light in vacuum is a universal constant. Also, it has wave-particle duality. So if the speed of light slows down in a different media other than vacuum, what exactly is slowing down? Macroscopically speaking, the speed of light does slow down. What about in the...
  17. Clay Gillespie

    Thought Experiment about light speed

    If we’re looking through a telescope at a craft we launched from Earth that is now passing Mars and send a radio signal to our craft telling it to turn on one of its lights on and it takes thirteen minutes for the radio waves to get from Earth to our craft how long will it take before we see the...
  18. M

    What happens if I speed up an Apollo group asteroid?

    Okay, having devised the antimatter bomb, I'm moving along to the concept of using Apollo group asteroids as freight trains for the inner solar system, but my knowledge of orbital mechanics is zilch. For example, (343158) 2009 HC82 appears to have a max speed of about 56 km/s at perihelion...
  19. G

    Pneumatic cylinder and working speed

    we have a pick & place application so please give the solution for that data cylinder stoke length 200mm, travel distance 200mm ,what is the picking time?
  20. SapientiaPT

    An experiment to measure the Speed of Light

    So, pretty much I want to make an experiment in order to get the speed of light. What I plan to do is to have a lantern in the dark(initially off) perpendicular to a wall, two sensors(one closest to the lantern and the other closest to the wall), then turn on the light making sensor 1 go off as...
  21. F

    Why is the speed of light smaller in a medium?

    Why is speed of light in matter medium smaller than speed of light in vacuum?Are all photons must be absorbed by atoms and then the atoms re-emit radiations in matter?What is real picture of all photons in transparent medium?
  22. H

    Speed measurement -- Limitations to "instantaneous" measurements?

    Is instantaneous limited to our in ability to continue to count time faster.
  23. Meruem

    I Observing a rotating body when approaching it at near light speed

    Summary: Will the motion around us become faster when we travel faster? When we approach a body rotating on its axis with certain speed v, will we see the body rotating in speed slightly more than the v during our motion ?And what happens assuming that we are approaching the same body in speed...
  24. M

    Can you help solve this Speed, Distance, Time Problem?

    Hi, I'm struggling to solve this problem. Can anyone please solve it and explain it to me? Thanks.
  25. Indula

    What's an Ion's sound speed (Cs) in a plasma?

    Summary: Is it the same as Bohm velocity ? Is it the same as Bohm velocity ?
  26. K

    Help calculating the uncertainty in the Sun's rotational speed

    Hi everyone, The equation is one we have been given to calculate the rotational speed of the sun for different latitudes. phi = average latitude. This shouldn't be a problem for me, but for some reason I just can't trust my error calcs. We are given : A = 14.713 ± 0.0491◦/d B = −2.396 ±...
  27. awer

    Best speed reducer for a simple project (gearbox design choice)

    Hi, As the summary says, I'm trying to design a simple gearbox with an approximate ratio of 20:1. I have two preliminary designs, one using a worm gear and another using a train of 5 spur gears. Both designs give me the desired ratio, but I really don't know which one I should choose. The...
  28. S

    Chemistry Calculation of average molecular speed

    We can calculate the average speed using this formula: uavg=root(8PV/ΠnM) I plugged in the following values: P= pi*10 atm (bar is approximately equal to atm) V=8lts n=2mol M=32*10^-3kg/mol But it is giving wrong answer. Can you tell me what went wrong?
  29. S

    Tension and speed of bowling ball pendulum passing the equilibrium position

    For part a I used conservation of energy. -m*g*cos(θ)*L+1/2*m*0^2=-m*g*L +1/2*m*v^2 => v = sqrt(2*g*L(1-cos(θ )). b) For b I was think that T = mg in the equilibrium point but that doesn't invole θ in the answer. So that's why I tought that T*cos(θ ) = mg. So that the tension is mg/cos(θ). But...
  30. P

    High Current 12V DC motor speed control

    Hi. I am new here. I have a question on how to speed control a DC motor running a pump. The pump is a seawater cooling pump cooling a large V8 motor. Therefore I need to control the RPM, based on the temp of the V8 Motor. Any ideas?
  31. R

    What if the Earth would have spin around itself twice as it's speed?

    Summary: What if the Earth would have spin around itself twice as it's speed? What would have be the consequences? How would has it affect the climate and living things?
  32. jk22

    I Lorentz Boost & Galileo Speed: Exploring Relationship

    What about if the speed parameter in a Lorentz boost were in fact related nontrivially to a Galilean speed ? More formally ##L(v_L)=G(v)\circ F## where L is a Lorentz boost with Lorentz speed ##v_L##, G is a Galileo transformation with speed ##v## and ##F## is still an unknown linear...
  33. nineteen

    Does speed of light depend on the wavelength or frequency of it?

    I heard that the speed of light doesn't depend on the wavelength or frequency of it, how does it happen? I don't understand it because the ultimate equation is c = fλ (where c is the speed of velocity of light, f is the frequency and λ is the wavelength of it...).
  34. S

    Find the speed of a copper loop falling in a magnetic field

    Hi all, so I had this problem and on the exam and I got a solution but I had an mass-term in there which wasn't given. I used Farraday's Law of Induction to get the Voltage induced. Then I used ##rho* \frac{A}{4a} ## for the resistance and divided the Voltage by that to get the current. I then...
  35. K

    Calculating Speed Between Two Cars

    Hi, I found a programming problem that calculated the speed between two cars as below and I would like to know how the calculation is done. it is about determining the speed of two cars. The coordinate reference system (y,x) is attached to the ego vehicle (as shown in the attached figure). The...
  36. Chandrakanth_balusa

    How is the turbine speed controlled by Grid but not by itself?

    Hello People, Greetings! i am back again with a confusing question for which I thought I could get a correct answer from here. so my question is regarding the speed of the turbine. I learned that the speed of a turbine has to be maintained constant in order to maintain generating frequency...
  37. M

    How to get the real object speed?

    I am trying to get the real object speed at a current moment. The movement is circular. I have all the timings. This is the data, the speed is in milisecounds, and the numbers represent the revolutions: 1. -504ms 2. -720ms 3. -1044ms 4. -1332ms I know the average speed of the object, at...
  38. S

    B Why is the speed of light limited?

    Summary: Why is the speed of light limited? Why does light have a maximum speed?
  39. N

    Engineering Calculating Efficiency and Speed of a DC Motor at Half-Load Torque

    First some basic figures which are very rounded as I'm interested in the approach to the problem rather than accuracy of the answer at this stage: The field current will be 500/220 = 2.2727 Amps, and so power is a fixed loss at 1136.36 Watts The armature current is 45 - 2.2727 = 42.72 Amps. At...
  40. S

    B What happens to speed and velocity in a rotating frame of reference?

    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...
  41. naji0044

    Inelastic collision problem: Bullet striking a wood block

    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...
  42. Sophrosyne

    B Speed of light with quantum path integrals

    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...
  43. Plat

    Radiometer rotation speed as function of pressure

    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...
  44. sadidrahman20

    Speed of falling object underwater

    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...
  45. Hiero

    I Does a beginning to time imply absolute speed?

    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...
  46. R

    Is the Speed of Light Really 3000 km/s?

    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
  47. andrea1313

    Terminal Speed of Vessel in Vacuum and Weightlessness

    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...
  48. S

    Force on a copper loop entering into a magnetic Field B with speed v

    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...
  49. S

    Spring is stretched, then attached to a mass, what is its speed at x?

    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...
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