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Questions tagged [distance]

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2
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3answers
63 views

Can length contraction help the moving observer reach a star system 'faster'? [duplicate]

Would an observer moving with close to the speed of light ($\sim 99\%$) towards a star system that's $20$ light years away perceive the distance as being less than $20$ light-years? If yes, how much ...
0
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1answer
34 views

Calculating the distance between two masses with respect to gravitational force [duplicate]

Call them $m_1,m_2$. They are compressed to their center of masses, if you wish. If the initial distance at $t=0$ is $d$, is there a formula or an efficient way to calculate the distance between them ...
0
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0answers
18 views

Launcher length require to reach a certain velocity [closed]

I have a UAV that I need to build a launcher for. Neglecting any sort of wind resistance, I need to calculate the distance it would take for the aircraft to reach 12 m/s. It has a mass of 5.5 kg. I'm ...
-2
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1answer
32 views

how to relate friction with speed and distance [closed]

Let's say that we push a 5g coin and it slides horizontally in a wood floor. if the friction is 0.74 and the speed is 1.5m/s , what will the final distance be?
9
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4answers
2k views

Are any of Euclid's 5 postulates false in Minkowski spacetime?

I often hear that Minkowski spacetime is non-euclidean. Euclidean geometry is characterized by Euclid's five postulates being true. Which of those postulates are untrue in Minkowski spacetime (if any),...
0
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4answers
93 views

Why is Work equal to Force * distance?

I totally get the mathematical part, but I cannot imagine how this works. I apply a force to a ball. Why does the distance over which it moves matter to me? Sure, if I calculate the kinetic Energy of ...
0
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1answer
67 views

Shortening of distances in Relativity Theory

I am studying relativity theory and I have understood why distances become shorter from the perspective of someone who is travelling close to the speed of light. However, later on I read that the ...
0
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1answer
29 views

Compare 2d metric to metric on sphere-puzzling result

I calculated the infinitisimal distance squared $(\mathrm{d}s)^2$ in 3d polar coordinates and 3d cartesian coordinates in an example to show that they were identical. I chose $P(r,\theta,\phi)$ as ...
1
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2answers
50 views

Are distance and displacement always frame independent?

I'm aware that distance and displacement, both are independent of reference frames, when the two frames are stationary wrt each other. Because the actual distance (or the shortest distance) between ...
4
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2answers
99 views

'Ambiguity' of dual vectors $\{dx^i\}$ in cotangent space in general relativity

The metric tensor is defined as: $$g = g_{ij}dx^i \otimes dx^j,$$ where I used the summation convention. We often omit the tensor product sign $\otimes$ and just write this as: $$g = g_{ij}dx^idx^...
0
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0answers
35 views

Negative Parallax - GAIA

In the GAIA DR2 release data, the parallax values are negative. I can estimate the distance for the positive values by theregular method of taking ...
26
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3answers
2k views

Why is the work done by a rocket engine greater at higher speeds? [duplicate]

From this comment by orlp: If I strap a rocket booster to a rocket in space and fire it for one second, then the work provided is much higher when the rocket is flying fast compared to when the ...
-1
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2answers
83 views

Is the astronomical magnitude identical to the distance? [closed]

Why do astrophysicists use Magnitude rather than the actual distance to calculate intergalactic parameters? The magnitude is the relative brightness and has no units, the typical distance requires the ...
24
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9answers
5k views

Why does work depend on distance?

So the formula for work is$$ \left[\text{work}\right] ~=~ \left[\text{force}\right] \, \times \, \left[\text{distance}\right] \,. $$ I'm trying to get an understanding of how this represents energy. ...
1
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0answers
50 views

Why are all the other sub-displacements included into to the total displacement? [closed]

Problem: During a jaunt on your sailboat, you sail $5\,\mathrm{km}$ east, then $5\,\mathrm{km}$ southeast, and then an additional distance in an unknown direction. Your final position is $20\,\...
-1
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2answers
104 views

Given Max Speed, Max Acceleration and Jerk - How do I calculate time?

I'm developing some python code that controls an end effector moving in a two-dimensional plane (XY). It moves through a list of points sequentially and I'd like to estimate the time it will take as ...
0
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3answers
35 views

Travelled displacement - how do we take care of the possibility that it might be negative?

so this is a very basic question but I can't really find a full answer. So let's assume we have a point of mass $m$ travelling along the x-axis with a acceleration a. The travelled displacement is: $...
8
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0answers
80 views

Does the trace distance specify a unique state

In quantum information, we frequently use the trace distance (see definition) to look at how similar two states are. If I had a known complete set of states $\{\rho_i\}$ and some unknown state $\...
2
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2answers
44 views

Can we determine the distance from a radio station (antenna) and a receiver using radio wave ?

say we have the a receiver and radio antenna can we calculate the distance between the receiver and the antenna by a receiver if we know the frequency ?
-2
votes
1answer
52 views

How loud would a sound have to be for it to travel the distance of Pittsburgh, Pennsylvania to New York, NY? [closed]

I'm just wondering if it's possible, more than anything. But if it is, how many decibels would the sound have to be to travel that far of a distance?
8
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2answers
2k views

How far can a shout travel?

I was wondering, if a person climbs a tower and shouts at the top of his lungs how much distance would the sound travel ? Would it reach someone 1km far? Assuming that there are no tall buildings in ...
5
votes
1answer
74 views

How much energy needed to cross the galaxy in time $t$?

Sorry if this is a dumb question. A friend of mine just asserted that it's possible to get anywhere in the universe in less than 30 seconds of your time due to time dilation. I do imagine that'll ...
1
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0answers
67 views

How far are we from the “edge” of the universe? [duplicate]

According the the Big Bang theory, the universe started as a 0-dimensional point of infinite density. Shortly thereafter, it underwent inflation and grew to some measurable size, and continues growing ...
1
vote
1answer
49 views

How accurately can the distance of a star be measured?

With the launch of the GAIA mission some years ago, a new precedent was set in mankind's ability to map our universe. However, how accurate are the distances created by this? From ESA's website, I ...
0
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1answer
209 views

Calculate distance an accelerometer moved

I am reading accelerometer data and want to determine the distance that the accelerometer is moved. ( My question is similar to the one placed here, Calculate speed from accelerometer . I just feel as ...
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0answers
35 views

Is there a difference between horizon and comoving distances?

I wonder if there a difference between horizon and comoving distances in cosmology ? I mean both correspond to a null geodesic $(ds^2=0)$ right ?
0
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1answer
70 views

The distance of an object undergoing constant acceleration

Is the distance an object moving increases with time if it is accelerated with a constant rate? I mean, doesn't it depend on the direction the object is traveling? if I throw an object upward, ...
-3
votes
1answer
40 views

Galactic Distances

I'm trying to show: 1 arcsec on the sky is approximately 5d parsecs at a galaxy, d parsecs away Could someone show me a proof of this statement, because it is bamboozling me!
1
vote
1answer
534 views

The difference between comoving and proper distances in defining the observable universe

"The radius of the observable universe is estimated to be about 46.5 Gly." If I understand correctly, it means the most distant object that we can see right now is 46.5 Gly away (at present), but it ...
0
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0answers
21 views

Calculation of distance modulus in cosmology [duplicate]

I have read that absolute magnitude is a measure of the luminosity of an astronomical object. Is there any mathematical relation between luminosity (L)and absolute magnitude (M)? And how apparent ...
10
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8answers
3k views

Does the mass of a bicycle directly affect stopping distance?

In this answer on the cycling SE, the claim is made that adding more mass to a bicycle increases the stopping distance. I was under the impression that mass should not affect the stopping distance so ...
15
votes
1answer
1k views

Inverse square rule for strong forces

Most of the forces induced by a point particle follows the $1/r^2$ rule. Then why does the strong force not obey it?
0
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1answer
44 views

Why are distances in cosmology larger with $\Lambda$?

I'm starting to study cosmology on these beautiful notes: http://www.damtp.cam.ac.uk/user/db275/Cosmology/Lectures.pdf . At page 16, when talking about distances in cosmology, the author says that ...
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2answers
75 views

What is the simplest way to find the distance of stars?

Once, I was staring at the sky and wanted to know the distance to stars I could see. I searched the Internet but didn't find any easy to use tools. The distance to stars can be measured using ...
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1answer
43 views

How calculate maximum distance for an Infrared floodlight

I got an IR-light 850nm which should radiate about 180m wide, The beam angle is 10°. I measured the following values with a laser power meter. ...
0
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1answer
48 views

How can distance and temperature be commensurable?

I am sorry to intrude. The discipline I know something about is metaphysics rather than physics itself. And on Stack Exchange I spend my time on English Language and Usage. I am struggling ...
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2answers
1k views

Distance and Displacement from a velocity vs. time graph

My teacher is saying that the distance covered will be equal to the area of the trapezium in the graph, but the displacement will be equal to the area of the triangle (with purple hypotenuse). I ...
0
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1answer
31 views

Different time for same amount of kph/mph change at different speeds

First of all excuse me if my english isn't perfect, and if the question is hard to understand, even I am a little confused about what do I even want to ask. So I bought a new wristwatch not too long ...
-1
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3answers
438 views

Distance traveled equals area under velocity time graph [duplicate]

I know that for the particular case where the velocity of an object along a straight line is constant, the area beneath the velocity as a function of the time passed curve equals to the distance ...
1
vote
1answer
233 views

Parallax versus Redshift when measuring astronomical distances?

From my understanding, the most common method for calculating how far away stars and galaxies are relative to us is by accounting for their redshift. I feel that this method could be inaccurate, ...
0
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2answers
207 views

How far can I spray water in a straight line from a pump knowing the pressure and flow rate?

I want to build a water gun (think super soaker) powered by a water pump. If I know the flow rate and pressure of a pump, can I calculate how far a jet of water will go in a straight line, assuming ...
0
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1answer
51 views

What is the relationship between heights and jet distance of water?

I'm doing an experiment on "Relationships between heights and jet distances of water". I used a bottle with a hole in it and change the height of the bottle as the column of water spout out of the ...
0
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0answers
115 views

Michelson Interferometer and distance

Previously using an interferometer, the wavelength of microwave radiation was measured. However if the wavelength was already known then the distance over which the reflector moved could be calculated....
0
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0answers
150 views

Distance from the center of earth to Lagrange point L1 (Earth-Moon system)

I have derived an equation for the distance from the center of earth to the L1. I have then used python to solve this equation (approximately). I have obtained a value of 326045071m (326045km). I ...
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5answers
271 views

Two cannons are fired from a boat, boat A is closer and boat B further. Which gets hit first?

A battleship (X) simultaneously fires two cannons towards two enemy ships. One close by (A) and one far away (B). The canon leave the battleship at different angles and travel along trajectories. ...
0
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2answers
42 views

Motion distance formula problem

I'm trying to learn physics from the ground up because I didn't have it as a subject in high school. Currently I'm studying motion. As far as I know and as far as my logic goes the formula for the ...
0
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1answer
25 views

How many magnetic latitude degrees would 100 km correspond to?

I'm trying to make a notation (an ionospheric plasma bubble) on a digram true to scale. I know the bubble is 100 km wide but the diagram has magnetic latitude and longitude for the axes. How many (...
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1answer
85 views

Frog jumping on a plank floating on water [closed]

I don't want you to give me the answer of the problem, I only whant to know how to think it. A frog of 200g is sitting at the end of a plank of 1kg and 1 m of length. The plank is at rest and ...
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1answer
811 views

How are the transverse velocity and proper motion of a star related?

For a star the proper motion, $\mu$, is usually measured in arcseconds per year. The diagram below illustrates how the quantities of radial, tangential and true velocity are related. The radial and ...
2
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2answers
93 views

What sound frequency can be heard the greatest distance by humans?

What sound frequency can be heard the greatest distance by humans? Assuming a pure tone, single frequency, same source SPL (dB) for each frequency, outdoors with no obstacles between source and ...