Questions tagged [speed]

Scalar quantity which is the magnitude of velocity.

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Speedometer Dilemma [closed]

This is what is written in Resnick Halliday Krane Physics Vol.1 The speedometer of a car indicates it's speed, not it's velocity, because it does not specify a direction. Speed is a scalar, since it ...
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Derivative of distance [duplicate]

I know that $speed = |\frac{\vec{dr}}{dt}|$ and first derivative of distance with respect time will be $\frac{d\vec{|r|}}{dt}|$ These 2 expressions don't seem to represent the same thing. But when I ...
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What is the speed of magnetic field in ferromagnetic, dimagnetic and paramagnetic materials?

If you have a very long(10k kms) rod made of a ferromagnetic material of diameter 1 inch, and u wind a coil on one end of rod to produce a strong magnetic field, strong enough to reach the other end, ...
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Speed of falling objects / with different altitudes

I have a question about gravity So as we know gravity is significantly less on high mountains or tall buildings and increases as we lose height ☕ My question is that if we have 2 objects with the same ...
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Isotropic speed of light verification [duplicate]

I have an idea for checking the isotropic speed of light in all directions that, as far as I can tell, does not involve clock synchronisation or mirrors or so called mechanical rigid bodies or ...
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Does equations of motion work for distance and speed? [closed]

In some books,when solving to find the distance and speed of the object having motion in straight line,the three equation of motion are used.so my question is whether these equation of motion (i.e $v=...
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Calculate uphill efficiency on different gears [closed]

I was interested to find whether it would be more efficient to climb a hill on a lower gear, so I did some calculations. I have the following data of a custom vehicle: Gear Drive force (N) Max speed (...
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Dependence of speed of sound [duplicate]

Why does speed of sound only depend upon elasticity of medium and not on frequency of vibrating particles of the medium?
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Why does force constantly change speed of an affected by this force object?

Force is counting in Newtons, and by its definition, 1 newton is the force affecting an object by the mass of 1 kg, changing the speed of this object by 1 m/s every second. I can easily make sure ...
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Is it possible make a train moving with less atmospheric friction if a pressurized air shield is applied at its frontal part?

Like the magnetic field blocks radiation particles approaching Earth could a pressurized air pipe at the frontal part of a train block atmosphere that constantly slows down that train? The pipe should ...
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What causes things to gain the speed of nearby gravitational sources?

While I’m aware that this probably has a really simple answer, I can’t figure it out. For example, humans, apples, but also things outside of earth like the ISS travel along with the earth, at the ...
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What is closing speed?

what is closing speed? the only information google was able to give me, is that closing speed is when a car is approaching another car both at 30m/s the closing speed is 60m/s, so what exactly is ...
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Why does the speed of sound in water not increase proportionately with temperature? [duplicate]

I was just wondering, as per this graph (https://www.engineeringtoolbox.com/sound-speed-water-d_598.html) why the speed of sound in water does not increase proportionately with temperature. Instead ...
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Out running a bear

I was going to ask this in wilderness but I’m pretty sure we’ll need some math to find out the real answer. They say you can’t out run a grizzly bear because they run about 35 mph. While the average ...
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Is Feynman right? Does mass change with speed? [duplicate]

In chapter one of Feynman's famous Lectures on Physics, he writes the following. Mass is found to increase with velocity, but appreciable increases require velocities near that of light. A true law ...
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Why can't any object gain the speed of light? [duplicate]

Suppose a object A is moving towards left with 200,000 km/s and objects B moving with 200,000km/s towards right. According to this above Statement, this could be happened because Speed of objects is ...
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Is the speed of objects in time, in Galilean Relativity, a constant and invariant speed relative to all reference frames?

(This question is only about Galilean Relativity. Not Special or General relativity.) Question: Is it true that every object in the universe, according only to Galilean Relativity is traveling in time ...
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Frequency and Wavelength of light in water [duplicate]

It is known that the speed of light is slower in water than in air. Does the frequency remain constant and on exiting the water, has the frequency changed?
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Is this expert report wrong about basic kinematics? [closed]

This question is about the application of kinematics in an expert report for Eirikson v. Breton, ABQB 2000 798 (archived), a judgement for a case where a woman was driving a car that was accelerating ...
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Simple difference between module of velocity and time derivative of module of position [duplicate]

What is the conceptually difference between the two: $$\frac{d|\vec{r}|}{dt}=\frac{\vec{r}\cdot\frac{d\vec{r}}{dt}}{|\vec{r}|}\neq|\dot{\vec{r}}|\equiv \bigg|\frac{d\vec{r}}{dt}\bigg|$$ ...
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Which of these is the beta factor in special relativity? [closed]

Obviously, $\beta=v/c$. But in this case, I'm not too sure what $v$ represents. I've mostly done 1-D special relativity and therefore it is pretty clear in those cases. However say there are two ...
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What is displacement time graph for this object which is in $xy$ plane going in sine wave like path from A to B. Also can velocity constant in path?

The path is from A to B in sine wave curve while the displacement is straight line.So how displacement is calculated for graph purpose here
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Earth colliding into planet-sized object faster than speed of light [duplicate]

Imagine the following scenario: Earth is travelling in one direction at just over half the speed of light Another planet-sized object is traveling in the opposite direction towards Earth, also at ...
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Does speed of electrons decreases when they pass through resistance?

What type of energy does battery supply to electrons , as I read battery increases KE of electrons but in load if they lose it then speed will decrease and current will decrease after coming out of ...
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Speed of sound in a real gas

The speed of sound in a real gas is $C = \sqrt{ZkRT}$, where $C$ is the speed of sound in the gas, $k$ is adiabatic gas constant $={C_p}/{C_v}$, $R$ is the gas constant and $T$ is gas temperature in ...
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In the case of a free wave function, does $|p| = E_k = 0 \mapsto |v|=0$?

This answer indicates that "it is not possible to talk about a particle 'stopping' or being 'stopped' in any meaningful or non-contrived sense" because of the Heisenberg indeterminacy ...
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Calculate efficiency from discrete power, time and distance

I have a sequence of points from GPS and OBD for some vehicles. Each point has the instantaneous power of the engine $(P)$, the time elapsed from the last points $(T)$ and the distance traveled from ...
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Why does kinetic energy increase quadratically by speed and linearly by mass? [duplicate]

I never found a simple explanation to kinetic energy and wonder if this one makes sense. In the following example, I'll try to provide an intuitional approach for calculating kinetic energy of an ...
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Is possible to achieve an infinite speed in real life? [closed]

Is possible to achieve an infinite speed in real life? I know beforehand that relativity theory forbids anything from travel faster than speedlight, so please stay with reading the full question first ...
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Why spinning bullet is more stable in air?

I found out about stagnation point recently, it is an arbitrary edge or point where the stream of air molecules parts. I was wondering could a spinning bullet affects the stagnation point to improve ...
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Is the sound speed and density relation different for compressible and incompressible media?

I'm studying "speed of sound in air" and I read that sound speed is inversely proportional to the density of the medium. However, I also know that sound travels fastest in solids, and that ...
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Average speed / Velocity

We know that in kinematics we have the concepts about "average speed". By definition the average speed is the total of the distance divided by time, but I still don't get it what is the ...
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Why does sound travel faster in helium than in air? [duplicate]

Sound wave travel faster in solid than in liquid, and travel in air with the slowest speed because solid is denser than liquid and liquid is denser than air. So, sound wave speed should be faster in ...
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We say that speed of sound is fastest in solids because particles are closely packed to each other, but why is speed more in hot air?now,they are far

I know we say that the speed of sound is most in solids because the particles are closely packed to each other,so,the energy transfer can take place easily compared to when they are farther in air or ...
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Why does the amplitude not increase the speed of the sound wave?

The way I see it,if there's a set up A which has 5 particles and another set up B which also has 5 particles,and assuming everything else is same in these set up,like distance between particles etc,if ...
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Would paradoxes arise if the one-way speed of light weren't $c$?

Introduction Let me start by saying that this is not a question about how to measure the one-way speed of light (OWSOL). It's about the physical implications of the idea that this speed is merely ...
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Why does the time of rotation only rely on the angle and the length of the string?

My question is in the title. How does the time of rotation in this example have nothing to do with speed? Intuitively, if the bob is going at a faster constant speed the time of rotation would be much ...
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1 answer
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If I had a car which could go with a speed of light, could I drive it at night? [duplicate]

Just theoretically, when I turn on the lights in my super fast speed of light car, would I see the road if the light can't go faster than my car?
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Will you see distance contraction inside the space ship at near light speed?

We know that distance to destination contracts for a passenger in a spaceship traveling at near the speed of light. If a spaceship is traveling at 0.865C to the outside observer, then the distance to ...
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Does gravity slow down sound (does sound travel faster downwards than upwards)?

I have read this question: So assuming the heavier planet has the same atmosphere as Earth, and that we can treat the atmosphere as an ideal gas, the speed of sound on the heavier planet would be the ...
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Speed of energy in a pulse wave

Consider a Dirac pulse giving rise to a wave propagating in a uniform generic medium. Since all mediums are dispersive and lossy except for vacuum, the frequency components of the pulse will travel at ...
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Could the kinetic energy formula $E=\frac{1}{2}mv^2$ be derived by the Pythagorean theorem?

The kinetic energy formula $E=\frac{1}{2}mv^2$ relates energy to the square of the velocity. There are many nice explanations on this site which deal with this fact. But could we give an explanation ...
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Can crooked surfaces alter speed messurement using a laser?

this might be an unconventional question yet I think the physics community would be the one to help here. Please hear me out. So my problem/question: I drove into a laser speed trap with my motorcycle ...
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Is it possible to measure the electric current speed through the wire by this method?

This method is very simple but I am not sure if it would provide accurate measurements.The current electrons deriving from the battery should have some speed and in that way should interact with the ...
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With what speed does a thermal front travel through a solid?

The heat equation provides theoretical temperature distributions as a function of space and time. Take for example an infinitely long rod that is suddenly heated up at $t = 0$ at its end $x = 0$. The ...
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Two waves having same wavelength

Is it possible for two wave to have same wavelength but different speed and frequency? According to $C=λ×f$, if wavelength is constant, then frequency must be proportional to speed. My explanation is :...
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Distance given two velocities

I have a home trainer that is connected to an application that I am writing which needs to calculate a distance traveled given the speeds that the trainer is sending. As such, every second, the ...
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1/velocity for higher dimensions

I have a somewhat basic question. I am sorry if it trivial. Denote the velocity by $v=\frac{dx}{dt}$ suppose that $x \in \mathbb{R}^n$ and I want to parametrize $t$ in $x$ and compute $\frac{dt}{dx}$. ...
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Does the mass in $E=mc^2$ change with the speed of the mass? [duplicate]

I was involved in a discussion on Quora about going faster than the speed of light and I pointed out that $E=mc^2$ implies that the faster the mass goes the more energy you would obtain from it. One ...
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At what speed would a wind affect a bullet? [closed]

Firing a gun loaded with the fastest bullet (.220 Swift 1,422m/s or any bullet that is super fast and excellent aero dynamics) in a close range (2cm) from the tip of an air blower. What would be the ...

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