Questions tagged [speed]

Scalar quantity which is the magnitude of velocity.

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1answer
34 views

Why is air resistance so counterintuitive?

By forming the ratio of the drag to weight, you find that it is exactly proportional to the ratio of the velocity to the terminal velocity. This gives the result that linear drag is negligible for ...
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Average speed and RMS speed, given speeds of objects

I am given the speeds of eight objects, and I have to find the average speed and the RMS speed of these objects. I tried taking the actual average of these speeds: $\frac{1}{8}\Sigma(v_i)$, but I get $...
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How can mean free path affect the propagation of sound in a gas?

I was thinking, since mean free path is a measure of "how long" a particle has to travel to collide with another, that this surely must influence sound propagation somehow. I would say this ...
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How do I find the RMS speed of the velocities of some objects? [closed]

I am given the speeds of eight objects, and I have to find the average speed and the RMS speed of these objects. I tried taking the actual average of these speeds: $\frac{1}{8}\Sigma(v_i)$, but I get $...
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7answers
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Can relativistic mass actually change gravitational pull?

I've heard that relativistic mass can influence gravity, but this seems to create a paradox, unless I am missing something. It seems to me that if there were two celestial bodies that are observed to ...
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Bow and Arrow problem '2'

Several days ago I posted the next question....Bow and Arrow problem. At the beginning the question got 3 downvotes but after a certain period it stabilized at equal number of downvotes and upvotes... ...
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Visualisation tool for different speeds? [duplicate]

I'm a student often doing kinematics word problems with objects moving at X km/h, Y m/s, or Z cm/s. Yet, I have no idea what these units look like in real life. Out of curiosity, I'm searching for a ...
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Conversion between pressure in PSI and velocity [duplicate]

My question is about whether you can convert the pressure something has to the velocity it will have. For example, if I had water shooting out of a hose at 100PSI, could I calculate the speed that the ...
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32 views

In a sine wave, what is the minimum possible distance between two particles which always have the same speed?

I was going through my book when I came across this statement which was stated as a fact. 'That the minimum distance between two particles always having the same speed is $\frac{\lambda}{2}$ where $\...
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Why is the speed of propagation of electrostatic force indifferent from the type of media?

Let say we have a charged sphere and a reactive material 1m away.If we introduce a media between them that attenuate the speed of the electrostatic force we should clearly see that the reacting ...
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Uncertainty in Speed of Light [duplicate]

In quantum mechanics, I know that there is an uncertainty in the speed of the non-relativistic particles (i.e. Heisenberg's uncertainty principle). Is there also an uncertainty in speed of light in ...
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Speed of momentum

I have recently played with a thought experiment for which I could not find the answer: Assuming I have a very long stick of several million kilometers and I pull one end: how long does it take, that ...
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Amplitude and speed of wave, energy conservation

I am stuck on following problem for days. "Calculate the dependance of amplitude on speed of the wave. Use the conservation of energy theorem." I need a little bit of help, how to I approach ...
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How to calculate number of turns and stops a car made from time speed and heading degree?

I have dataset that looks like this but more rows and need to have a function to return number of turns and stops during this trip.
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Doubts related to speed of sound in different mediums

since childhood we have been taught that sound travels faster in solid (most dense) as compared to liquids (less dense). and speed of sound is greater in liquids as compared to gases (least dense), ...
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1answer
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Is it theoretically possible for a proton to travel fast enough to destroy the sun by virtue of its relativistic mass?

I realise this is a (slightly) nihilistic question but lock down and all... Is it possible to destroy the solar system by launching a proton at the sun at a speed approaching c (as seen in cern 0....
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Two values to the speed of light …what does this mean in the real world?

If $E= mc^2$ then c = $\pm \sqrt{E/m}$. What is the real world meaning for a negative speed of light ? Anything traveling faster than $-300k m/s$ is travelling faster than the speed of light ? What ...
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What's the speed of force? [duplicate]

Brain storm: Suppose we have a perfect lever, which has 0 quality, and perfect rigidity. It is long enough that can reach Proxima Centauri from the earth. Someone push one side of lever from Proxima ...
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Are the speed of sound and water ripples' speed the same?

When a droplet of water hits the surface of a lake it produces ripples that travel outward. My conception is that it travels at the speed of sound in water (since sound are nothing less that ...
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What's the speed of the train with our point of reference being the person who's moving inside the train? [closed]

A person moving in a train with the speed of 1m/s to the right, while the train is moving in the same direction with the speed of 10m/s From the person's point of view "considering that the ...
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Thermal velocity vs speed of sound

Is it possible that for a gas, speed of sound$>$thermal velocity? I cannot imagine it since, for the ideal gas limit, the interactions solely rely on the bouncing back of molecules
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1answer
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The distance between two moving objects at the speed of light [closed]

Two objects move in the same direction at the speed of light. If we look at one of these two objects, what does the distance between the two particles change? Does it stay the same?
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2answers
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Estimation of greatest speed in a polyhedron

in order to control velocities in a three dimensional volume, I look for a proof or a proof idea for the following assumption: Given a non-empty solid polyhedron in 3D, all points inside this set ...
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232 views

The mathemathical physics behind punching things that hang

How do you calculate the angle at which a hanging body will move when it is hit on it's hanging end?
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Is this intuition correct? (dot product)

So, it is based on the article below: Go to the bottom of the article where the 'Mario-Kart Speed Boost' example is. So, the intuition in the examples makes sense to me but sometimes people explain ...
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1answer
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Is there a difference between instantaneous speed and the magnitude of instantaneous velocity?

Consider a particle that moves around the coordinate grid. After $t$ seconds, it has the position $$ S(t)=(\cos t, \sin t) \quad 0 \leq t \leq \pi/2 \, . $$ The particle traces a quarter arc of ...
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Need some help understanding velocity

I have just started learning kinematics and this is just a small question, that I wish for to clarified as it feels a little bit confusing. Below, the difference between speed and velocity is given. I ...
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Is there any difference in hitting an empty wall vs a full wall with the head, considered the surface is the same? Which one is more painful? [closed]

It sounds to me like empty objects are less painful, but not sure why and what is the physical reason for this. I also tried an experiment where I was throwing eggs against two different walls, but ...
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1answer
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What is the direction and orientation of a pendulum's acceleration at the ends of the oscillation? And at the midpoint? [closed]

A simple pendulum (a body oscillating at the end of a wire) describes an arc of a circle at each oscillation. What is the direction and orientation of the body's acceleration at the ends of the ...
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1answer
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What does graph of a function mean?

I'm asked to do a graph for the speed of the rocket as a function of the flight altitude. Here are the values: h (m) 0 4 13 32 55 83 103 and v (m/s) 0 4 7 12 16 20 23. Does this mean that the flight ...
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What is the difference between two types of velocity?

What is the difference between $v=\frac{s}{\Delta t}$ and $\bar{v} =\frac{\Delta\bar{x}}{\Delta t}$, are they the same?
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Why do we need instantaneous speed?

I am new to this topic and was just wondering about the use of instantaneous speed. I mean, we use to calculate the speed of car let us say at 5 sec. So we take the distance travelled in 4.9 to 5.0 ...
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Does an Optical Diametric Vacuum Solenoidal Drive could prove itself against information speed limit?

About these two publications, I came up with a different answer an ask for validation. The scissor paradox: can we pass the information faster than light? Is it possible for information to be ...
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Measuring a speed in Kelvin $K$

Since the Kelvins are a temperature unit and temperature is basically molecule/atoms excitation (so they have a "speed of excitation"), could it be possible to measure a speed (let's say 10 ...
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3answers
292 views

How can a bicycle keep its momentum while changing direction?

I was riding my bicycle downhill. When the street leveled I realized I had forgotten something so I started turning around without pedaling, pretty much using the momentum I had acquired. Soon I was ...
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Speed of light during reflection [duplicate]

Does light hitting a mirror stop before being reflected. And if so does it have to accelerate back up to the speed of light. In other words, when light is emitted by any means is it instantly ...
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1answer
56 views

In general relativity, if an object has no speed is it then not affected by gravity? [duplicate]

The way I understood general relativity is that there is no force of gravity but instead all object just move forward but the space they move through is distorted and that's why their trajectory seems ...
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What's the terminal velocity for an air bubble in water?

If you release an air bubble sufficiently far under the surface of water, what is the terminal velocity of the bubble that is created? Is the terminal velocity contant or varying (the size of the ...
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Based on Newton's law of universal gravitation: How fast does any gravitational disturbance propagate?

Based on Newton's law of universal gravitation: How fast does any gravitational disturbance propagate?
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We know a human cannot run on water, but could a much stronger and faster animal?

We know a human cannot run on water, but could a much stronger and faster animal? This viral video shows a moose running across a body of water: https://www.youtube.com/watch?v=K5-0d00hV1c Some say ...
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How certain are we that and objects spacetime speed is constant

I just recently realized - through the aid of a simple yet effective video - that mass curves not space, but spacetime. This has lead me to finally understand why we use geodesics to explain the ...
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What is mach number = 0?

If you look at a paper on fluid dynamics, you will see a paper that is performing CFD simulation with a mach number of 0. This means that the flow velocity is 0, so I thought that no flow would occur, ...
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Is it possible to find relative speed?(its speed not velocity)

I was wondering that relative velocity can be computed easily due its directional nature. but what about speed? Speed is not directional so now we cant find relative speed of objects in different ...
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One-way speed of light experiment

Ok, this is (probably) my last question about this topic. My other two (here and here) had some misguided assumptions, but I think this one is better. (There is probably something else I am neglecting,...
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Measuring the one-way speed of light?

I know many people (including me) are bombarding this site with questions about the recent Veritasium video about the one-way speed of light, but I think I found a way. Here it is: (You can see sort ...
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Term for travel time per distance

Does the physics community have a term for the time per travel distance, $dt/dx$? I.e. the reciprocal of the speed. Runners call this their pace.
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How do waves of sound look like emerging from a massive rectangular block if the horizontal speed of sound in the block varies?

Suppose we have a rectangular block of material (length $l$, breadth $b$, and height $h$) lying horizontally on a surface. We apply a horizontal and uniform vibration of a single wavelength(by ...
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108 views

For vertical circular motion, why does the minimum speed for a full cycle depend on what the ball is attached to?

Suppose we have the following situation and I'm asked for the minimal speed to be given to the ball so it can continue a full cycle. If the ball is connected to the middle point with some hard ...
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1answer
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Train speed and closed windows

Most coaches in Indian trains are non-air-conditioned, i.e., the windows can be opened. Recently, the government has planned to convert all coaches in some trains to A.C., citing the fact 1 that for ...
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Data for experiments of Doppler effect

I am a high school student that has attempted to carry out the experiment for the Doppler effect using an RC car going at constant speed, a sound source at constant frequency and phyphox app to ...

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