Questions tagged [speed]
Scalar quantity which is the magnitude of velocity.
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Does weight affect the drag force on a falling parachute?
In my physics class we currently have to do research about a motion and preform an experiment and write an essay on it. The idea I had was to drop two parachutes with different areas from the same ...
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Correct definition of “speed” of gravity
Traditionnal definition of speed in space-time
If I understood it correctly a speed is defined relatively to space-time, i.e. we can talk of the speed of anything moving or propagating “inside” space-...
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Why does the speed of sound decrease with increase in density?
In my book it's written that speed of sound will in increase with increase in density of the medium as molecules with get closer to each other, but after some browsing on internet I found out about ...
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1answer
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How (and why) is energy due to friction independent of speed?
Consider a rotating disk and a fixed part that "abrades" something. Under normal conditions the disk and the fixed part should not touch. However, they slightly touch due to misalignment. When the ...
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What does the first derivative of (2-norm) distance with respect to time tell us?
My basic physics' knowledge is a little rusty. My apologies in advance. I know that the first derivative of position or displacement with respect to time is the instantaneous velocity. Suppose I have ...
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1answer
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Is combustion engine power defined by speed and torque?
Of a combustion engine, the speed, torque, and power is measured at the crankshaft.
For a measured pair of values for speed $N$ and torque $M$, can there be more than one value for power $P$? In other ...
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2answers
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Do Lorentz transforms use velocity or speed?
Suppose we have the $S'$ frame moving at some velocity $v$ in the $X$ direction relative to the $S$ frame, then it follows
$$x' =\gamma (x+vt), t'=\gamma(t+\frac{vx}{c})$$
From my understanding, to ...
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What if the directions of the initial and final velocity are different in the conservation of mechanical energy equation?
I saw a problem, and saw that it could be easily solved using conservation of mechanical energy. So I wrote my equation:
$$mgh_1 + \frac12mu^2 = mgh_2 + \frac12mv^2$$
Where $u$ is initial velocity, $...
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Does time travel faster than the speed of light? [closed]
I don't know enough about the subject to know that I am wrong.
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How fast in mph is water when released from dam, a point of exit , as a baseball is clocked in mph when released from a pitchers arm [closed]
How fast in mph is water when released from dam, at point of exit , as a baseball is clocked in mph when released from a pitchers arm .
I am a complete novice and looked all over for an answer
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When does gun barrel length become too long with a constant pressure?
Just struck out of curiosity,
It is a fact that longer gun barrels do increase the acceleration of a projectile, but an infinitely long barrel does not give infinite acceleration. So then, with a ...
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13answers
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Why don't we use rapidity instead of velocity? [closed]
In school we learn that we can add velocities together, and then later on we learn that it's not correct and that there is a speed limit. Why create all this confusion when we could just use rapidity ...
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Doubling winch force to gain speed - is it possible?
It's very common to use pulleys or snatch blocks to double the "winching power" - reduce the force needed to move a particular load, at the expense of the speed, given a constant winching rate.
...
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2answers
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What would happen if I rotated an extremely long stick? [duplicate]
(Exclude all movements of myself) Imagine I had a straight stick that reached far out in the universe.
If I rotated that stick, what would happen to the speed of the stick and its shape?
(First ...
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1answer
45 views
Do all particles with zero rest mass and finite energy have to travel with speed of light in vacuum?
Suppose there exist particles with zero rest mass ($m_0=0$) which are not photons. Let them have a non-zero finite energy $E$. Do they also, just like photons, travel through space with the speed of ...
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1answer
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Behavior of sound on interface of 2 media
We say that sound travels faster in steel than in air. Thus if we want to know whether a train is approaching us we can put our ear on the rail track as we would be able to hear that quickly.
Now ...
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2answers
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What saves bike rims when one rises before hitting small obstacles at full speed?
Statement 1: "A race car weighing, say, 1000kg has an "effective weight" of only a few kilograms when it cruises at a speed of, say, 200km/h."
Statement 2: A road cyclist with a combined weight (...
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1answer
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Relative velocity of a particle under uniform circular motion
The question is based on fairly simple mechanics principles but seems to have no definite answer.
Suppose there is a point particle A at a point X and around it another particle B in uniform circular ...
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3answers
71 views
Why does frequency remain the same when waves travel from one medium to another? [duplicate]
I was reading about reflection and refraction on BBC Bitesize and I can't understand why frequency is a constant in the wave speed equation. I can't visualise the idea of it. I know that wave speed ...
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1answer
32 views
How force affect the objects that we apply on? [duplicate]
Why do things get accelerated rather than do a moving at constant speed when we apply a force on them? How my force affect the object at atomic level? Does it increase the kinetic energy of atoms ? If ...
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Is there a physics law according to which, in general, the smaller an object is, the faster it moves? [closed]
I have always felt, in general, that dogs run faster than humans and that birds fly faster than dogs and than bees can fly or at least drift by the wind faster than birds and that plant seeds would ...
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Speed of sound in ideal gases
The equation of state for an ideal gas is given by:
$$p = \rho r T \tag{1}$$
In the other hand, the speed of sound is calculated by:
$$c = \sqrt{{\partial p\over \partial \rho}}\tag{2}$$
Using (1) ...
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2answers
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Why is the energy probability different from its speed probability in the Maxwell-Boltzmann Distribution?
I know this has been asked before here and I understand how the formula changes when the Maxwell-Boltzmann Distribution (MBD) is written in terms of speed. But I am trying to understand this more ...
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Does the speed at which a chain is pulled in vacuum of space, matter? [closed]
If I pull a very long chain attached to a 50 pound dumbbell at $1000 \; mph$ in the vacuum of space (assuming we are uninfluenced by gravity), will the chain break? Take a steel chain for example. The ...
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1answer
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Does the effect of gravity get slower at high speeds?
If a sentient object was vibrating at near light speed and was some distance off the ground. Compared to being relatively stationary to the ground, would it take a longer while for them to fall down ...
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Why do we experience more centripetal force when we make a sharp turn compared to a wide turn? [duplicate]
If $F=m\omega^2r$, why do we experience more force when we decrease the radius of the turn?
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5answers
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How to explain the Maxwell Boltzmann distribution graph (physically)?
While studying the kinetic theory of gases, I came to the section: "The Distribution of Molecular Speed" of a book. The book first (without any explanation) proposes the Maxwell's speed distribution ...
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2answers
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How is the root-mean-square error related to the confidence interval?
If the car's speed is calculated as V = 100 km/s, and the RMSE of V is 20 km/s.
Does that mean V = 100 +/- 10 km/s, or V = 100 +/- 20 km/s?
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How much at least should the Earth be smaller so that we notice these three phenomenons?
The Earth is moving with a speed of about $1670$ $km/h$ around its axis. This speed is more than the sound speed. So the Earth is always breaking the speed of the sound. How much at least should the ...
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1answer
36 views
What is the speed of Pushing/Pulling? [duplicate]
If there was a huge rod the length of a light-year in space and someone pulled one end of it, when would the other end move?
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1answer
60 views
Determining acceleration in order to meet a space-time-velocity reservation
An Example
A train on a single line track is told to be at position $x_{res}$, at time $t_{res}$, and to be moving at exactly $v_{res}$ when it hits that point. Where $_{res}$ denotes the reservation....
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Why do macroscopic objects not move at the same speed their constituents are made of?
How can subatomic particles move at relativistic speeds while the things they make up are moving much slower?
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1answer
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What is the relation between the fundamental frequency and a harmonic?
I am currently busy with a physics report about determining the speed of sound in air. In order to do this, I was told to use a tube that can extend or shorten in order to find the different harmonics ...
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1answer
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When was the speed of a bullet or cannon ball first measured? [closed]
I see that prior to the invention of accurate clocks it might have been pretty hard and I wonder, just as with the speed of light, the speed of bullets was wildly over-estimated.
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1answer
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Measuring the solar system's speed through ether with the help of an eclipse
In A.P. French's Special Relativity, the author said,
Jupiter has
a period of $12$ terrestrial years, and so in half a terrestrial year,
while the earth moves from $A$ to $B$ (Fig. $2$-$7$), ...
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3answers
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Do photons actually slow down in a medium, or is the speed decrease just apparent? [duplicate]
Some places I've read flat out say light actually slows down in a medium, some say the speed decresae is just apparent but not real and that the photons still travel at the constant speed of light.
I'...
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1answer
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Maximum Speed for Space Travels
Considering a hypothetical spaceship that has an unlimited amount of fuel, traveling within the solar system planetary plane, what would be considered a safe maximum speed for traveling around ...
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2answers
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Time taken by a boat to stop with its engine turned of moving in a lake [closed]
The question is taken from I.E.Irodov and it states that
A motorboat of mass $m$ moves along a lake with a velocity $V_o$. At the moment $t=0$ the engine of the boat is shut down. Assume the ...
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5answers
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Speed of light and speed of sound in the same medium
Can anybody please tell me if there is an established relationship between the speed of sound and speed of light when they are traveling in the same medium? Are they related to each other in some way?
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1answer
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How does the change in speed of sound affect our perception of pitch?
Let’s say the speed of sound is 343m/s and thus the wavelength of the note with frequency 440Hz is about 0.78 meters. If I played the same note through a medium where the speed of sound was doubled to ...
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How to think about speed or velocity of an electron (in an atom)?
One answer to this question explains that "velocity of electrons has no meaning" while another says that "it can be argued that they don't move around atoms at all". And then in another post it is ...
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Do electrons have intrinsic speed?
Absolute zero is the point at which the fundamental particles of nature have minimal vibrational motion, retaining only quantum mechanical, zero-point energy-induced particle motion.
At absolute zero ...
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What will limit Santa's top speed in traveling between two major cities on opposite sides of the planet?
My school is hosting a family night, and the math department has charged me with setting up a booth where visitors can grab a yard stick and a world map and, given Santa’s top speed, calculate how ...
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1answer
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How does observed black body radiation change with observer speed?
Black body radiated power is
$$P =\sigma T^{4} \tag{1}$$
and temperature in a gas is related to particle speed as
$$ T = \frac{mv_{{th}}^2}{3k_{B}} \tag{2}$$
where $v_{th}$ is the root mean ...
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Relativity Of Simultaneity Confusion
I have currently been introduced to relativity of simultaneity with the following thought experiment:
Consider a train in which there are two presidents, one sitting at the front and the other at the ...
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5answers
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If it is impossible to travel at the speed of light, then what is the theoretical max speed a spaceship could go? [closed]
I'm just pondering this so I can ask another question intelligently. Thank you
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What is the upward speed needed for a body to float near Earth's surface?
I want to know the velocity that a body needs to i.e literally float near Earth's surface assuming gravitational acceleration is 9.8 m/s² everywhere on the planet and the body is 1m away in altitude. ...
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1answer
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Does speed affect space?
Since gravity can affect time, speed can affect time, what would a high amount of kinetic energy look like on a model for the fabric of space? Such as with the models of bent space beneath planets, if ...
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0answers
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Heat generation of a high altitude object at high speeds
I'm developing a game in which I need some calculations for heat generation due to atmospheric friction. I'm aiming to write a quick python script that calculates approximate heat levels at 10km ...
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1answer
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Distance in seconds between moving vehicles
If two cars are moving in the same direction.
let’s say ego car is in the front and another follower car. the speed, location in x, y coordinates of both cars are given.
How to calculates the ...
