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Questions tagged [speed]

Scalar quantity which is the magnitude of velocity.

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What is the distribution of speeds in an ideal liquid?

By ideal, I mean similar conditions to the ideal gas-in-a-box with perfect spherical perfectly elastic homogenous atoms, so no inter-atomic forces, evaporation, gravity, rotations or phase changes. ...
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The speed of a QM particle

In the original theory of quantum mechanics what is the speed of quantum particles, I am asking this because photons can only travel at the speed of light C. What about mass particles?
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How significant is the parabolic arch effected with an incline versus a decline in angle versus a decline in angle . For example throwing a dart

A dart players height can vary as can the height in which they raise their arm to aim. Is there less parabolic arch when throwing at the same strength from above the target compared to below, due to ...
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Sound Timing: Stationary vs. Moving Source - Who Wins?

Case - 1: A stationary source emits sound and an observer stationary is at 'd' distance apart. Case - 2: A moving source emits sound when an stationary observer is at 'd' distance apart. Will in both ...
Sam Tunkaho's user avatar
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Friction acting on a moving car

I am trying to understand the nature and direction of friction force acting on from the ground a car driving up an incline. I was thinking about a simple situation where a car of mass $ m $ is driving ...
Lukasz Skowron's user avatar
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Is the drag coefficient linear with speed?

I made an RC-car and wanted to simulate the drag of it in Solidworks. But after I did my simulations I put my results in a graph, the drag is quadratic with speed but the drag coefficient $C_D$ is ...
BobTheBuilder's user avatar
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Can you make a car powered by 4 car air jacks? Using the mechanics of a manual pedal pottery wheel

If an air jack can pump up a car using little force, can’t an aluminum air jack spin a plastic wheel barrel car going at least 10 mph? Each wheel will have an air jack that uses the mechanics of a ...
DevGabe's user avatar
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Speed is equal to distance divided by time but is this correct?

In this study https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9784821/, the distance the punch travelled from start to impact is 0.49 meters and the time taken from start of punch (that's it, they define ...
SnoopyKid's user avatar
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Is there a different way to measure speed, other than with time?

A second on Earth is different from a second on the Sun and a second next to a black hole. Therefore speed, as measured in meters per second, is different in each of these locations. Is there an ...
foolishmuse's user avatar
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How fast does information travel through air molecules?

You're always told that information travels through air (speed of sound) at appx. 767 mph. This doesn't tell you how fast the transfer of momentum happens between the actual molecules of air. So how ...
Wyatt's user avatar
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Is it possible to have a uniform speed but variable velocity in one-dimension motion?

Is it possible to have a uniform speed but variable velocity in one-dimension motion? I saw a lecture where teacher said that it is possible if particle changes its direction of motion 180$^\circ$. ...
NOTE Book's user avatar
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Rotational speed using conservation of angular momentum

I know that angular momentum is conserved, but I don't know how to calculate the new speed of an object after it shrinks. Say you have a spinning object, then it shrinks, then how do you calculate the ...
Astrovis's user avatar
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Why is velocity used for kinetic energy instead of speed? [duplicate]

This may seem like a self-explanatory question, but if kinetic energy is a scalar quantity, and squaring the velocity essentially removes its vector quality, why not use speed instead? I have a hunch ...
Ephemeralist's user avatar
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In this conservation of momentum problem, where is the sign error coming from?

Say I have a particle travelling in the $x$-direction and breaking into two pieces: Conservation of momentum in the $x$-direction obviously gives: $$mv = m_1 v_1 \cos(30) + m_2 v_2 \cos(60).\tag{1}$$ ...
Allure's user avatar
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Northern lights / aurora borealis "pre-warning" - how does this work w.r.t timing and different particle / wave speeds?

There is an article in the newspaper today entitled "Northern lights predicted in US and UK on Monday night in wake of solar storms". I assume that the reason that someone can make this ...
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Who wrote $c = λ ν$ for the first time and where can I find it?

I have been surfing for days and still I could not find who wrote the equation $c=λν$ for the first time. Neither I found a name for this equation. A lot about Planck's constant and energy related ...
Pierpaolo Testavuota's user avatar
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2 answers
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Average velocity showing different results

I was solving a question, in which, a particle has travelled a distance $s$, with initial velocity $0$ and constant acceleration. So the equation of motion becomes, $$ v = a t \tag{1} $$ and $$ v = \...
Agent_A's user avatar
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How does a seatbelt help in a car crash? [closed]

If you are in a car crash, you will likely have on a seatbelt because they are supposed to help you from getting injured/harmed. But, I don't think they are that much of a help. First of all, say you ...
Kellan Heerdegen's user avatar
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What is the equation for the speed of a molecule at a specific temperature?

What is the equation for the speed of a molecule at a specific temperature? I saw two equations $v = \sqrt{\frac{3 k T}{m}}$ and $v =\sqrt{\frac{3RT}{m}}$. What is the difference?
Arjun Raj's user avatar
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Why isn't the tangential velocity of circular motion zero?

Why is tangential velocity 2πr/T if the body's total displacement in the end of one revolution is zero?
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Instantaneous speed x instantaneous velocity

Related to Distinguish between instantaneous speed and instantaneous velocity I understand that the average velocity is given by the displacement divided by the change in time, and it is a vector ...
Quiet_waters's user avatar
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How to calculate the time derivative of electromagnetic field? [closed]

How can I calculate the time derivative of an electric field from its space derivative? That is, I know $\frac{dV}{dx}$, and I need $\frac{dV}{dt}$. In general, $\frac{dV}{dt}$ = $\frac{dV}{dx} \times ...
katang's user avatar
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Question about light and distance

If we see into the past with light and distance travelling so we can’t see things how they are currently, only how they were in the past; and James Webb took a photo from the beginning of the universe ...
Mary Cox's user avatar
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3 answers
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What's the limit on the length of string that can be pulled by a person? [closed]

Imagine it's pre-industrial times, and a king wants to keep control of his vast empire. One of the biggest problems was how slow it was to transmit information; it could take weeks to be notified of ...
Reuben Matthews's user avatar
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Why is it that objects inside a moving train tend to move at the same speed as the train itself?

I mean I get people saying because it's Newtonian mechanics. Everything inside the train will have same speed as that of train but my question is why ? Why is it like that ? And How does that happen ? ...
S.M.T's user avatar
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What's the fastest speed water from a glacial dam burst could achieve? [duplicate]

I've been watching a lot of Graham Hancock videos of late, thrusting myself deep into the rabbit hole of pseudoarchaeology/alternative archaeology, and I don't really know enough to assess the ...
Josh Hills's user avatar
-1 votes
1 answer
148 views

What does instantaneous velocity mean? [duplicate]

What does instantaneous velocity mean? on google it says "Instantaneous means something happens very quickly, in a single moment. It's similar to the meaning of "instant", but most ...
Intensed's user avatar
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What would happen to a person's body if they were struck with a meteorite?

Considering that this is a meteorite that has broken through the Earth's atmosphere, what would happen to one struck by a meteorite? Not a large one of any sort, but one around the size of a fist. How ...
CrimsnComet's user avatar
2 votes
1 answer
110 views

Can field itself have a speed?

I've seen many examples about a particle moving relative to field. But I never saw a field moving relative to observer (or a particle). So, can field have a speed? I thought about some possibilities: ...
Song's user avatar
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Speed of sound confuses me

Just a random question out of interest. When you hear an explosion, e.g. a firework, firecrackers etc, from far awa how does the sound reach our ears so quickly? The speed of sound in air is like 300m ...
PepegaAskingQuestions's user avatar
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The proportionality of a Drag force and speed

At low speeds, Drag force is proportional to speed due to Stokes law. At higher speeds, Drag is proportional to the square of speed. While modelling the speed of a water rocket, I realised that when ...
user136808's user avatar
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Product of two 4 positions without writing the components

I was able to solve the first part of the following question by expanding the terms as vectors I can't understand how to do it without expanding so I had a look at the answers. I understand how we ...
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How can we accurately tell distances of celestial bodies when considering superluminal expansion [closed]

If parts of the universe are moving away from each other faster than the speed of light relative to my position in space, how can we accurately tell the age or distance of other celestial bodies ...
Spatium et Tempore's user avatar
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Funneling air into a small opening, calculating time of speed differential

Assume I have a funnel that fits a rectangle air vent of 1" x 4" with an opening for a circular tube of 0.5" diameter. After connecting a 0.5" diameter x 2 ft tube to the funnel, ...
Jchen's user avatar
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2 answers
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How can light have a speed when it devies what speed is?

For us to measure any movement, the "something" has to have a different position to some reference frame. now speed is defined by the amount of changed position( which we can tell by the ...
michaeloppenheimer's user avatar
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1 answer
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What's the speed limit for things with mass?

So the speed limit of the universe is 299 792 458 m/s, but only massless things like photons can archieve this speed. Since things that have mass can reach 99.99999...% speed of light, does that mean ...
comp_guy_dude's user avatar
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Why is it more difficult to turn the steering wheel of a stationary car than a moving car? [duplicate]

I believe anyone who has driven a car without power steering has noticed this effect. I am not able to find a justifiable argument online. My thought process suggested it must have to do something ...
Avish Bhatia's user avatar
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2 answers
90 views

Why does force decrease with increase in velocity in case power was constant?

Suppose an internal combustion engine burns the same amount of fuel every cycle (regardless of engine or car speed ) that means it creates the same pressure every cycle and the force on the piston due ...
John greg's user avatar
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Reality of speed and time [closed]

I have a very simple question. How does a faster object takes less time for the same distance? A car with a speed of 100km per hour takes one hour to travel 100km while a car with the speed of 50km ...
majid dadmand's user avatar
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How long does it take before neutrino velocities in the neutrino background radiation are substantially less than the speed of light?

The energy of photons is reduced by the expansion of space. Since the photons have been decoupled from matter their wavelengths have decreased from the visible range to the radio range. The same ...
Il Guercio's user avatar
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1 answer
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What are the exact conditions for the constancy of the speed of a wave?

Do two mechanical transverse waves traveling in the same medium have the same speed whatever the source might be? If the answer to this question is yes, can I generalize and say "all waves of the ...
Jack's user avatar
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In circular motion is acceleration vector and $\frac{dv}{dt}$ the same?

I was studying a book in which they have written this $$ a = -w^{2} r \hat{e} + \frac{dv }{dt} \ddot{e} \tag{1} \label{1}$$ Where $a$ is acceleration vector $\hat{e}$ is unit radial vector and $\ddot{...
Uttkarsh Saini's user avatar
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1 answer
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If mass was to reach the speed of light it becomes infinitely heavy. Does this mean it has become a black hole singularly? [duplicate]

If mass reaches the speed of light, it becomes infinitely heavy. Does this mean that it has become a black hole singularly?
Morbo Guano's user avatar
4 votes
3 answers
356 views

Why the free Lagrangian does not dependent on the velocity vector direction, only its speed?

For freely moving particle, It's said $L$ can't depend on the velocity vector, but only its magnitude. Question: I'm looking for the contra-argument. Let's say $L$ depends on velocity vector. Then, ...
Giorgi's user avatar
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What does the square in kinetic energy formula imply? [duplicate]

I was wondering if the velocity squared imply that you need exceedingly more energy to gain speed. And if so, why is this a thing?
Dhari's user avatar
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2 answers
211 views

Average angular velocity and speed

Are the magnitude of average angular velocity and the value of the average angular speed always same? If not then can you please give an example.
Sanjay's user avatar
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How long does it take to hear the sound of a plane that travels at the speed of sound?

in our physics lessons we often learn how to calculate the time that sound of a plane that travels faster than sound takes to reach us using the Mach cone. But can we use the same method to calculate ...
Chamodh Nethsara's user avatar
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1 answer
310 views

How Long For An Object To Catch Up To Another Object Moving At Different Speeds? [closed]

Example: A bear is 10 m away from a person, the bear is moving at a speed of 15 m/s, the person is moving at a speed of 6 m/s, how long would it take for the bear to catch up to the person? I'm not ...
burner8268's user avatar
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How fast can the human hand move?

I was playing with my six year old daughter the other day with her toy airplanes (I’m a pilot and she’s very interested in aviation now). I took the little F16 toy and flew it passed her as quickly as ...
Cjh199712's user avatar
1 vote
5 answers
156 views

Speed and Velocity

Why did physicists develop the concept of velocity? I searched on the web, but I didn't get a satisfactory answer. All I got is that velocity has a direction whereas speed does not. Why do we need ...
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