Scalar quantity which is the magnitude of velocity.

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2answers
69 views

Where does energy go when performing a useless effort?

I went to school one day, so I thought I was able to get this simple one.. but it looks like I'm not anymore. :( One lonely little spaceship is resting into space. It has a small fuel capacity that ...
2
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1answer
41 views

How fast do molecules move in objects?

I guess it depends on the heat or the type of the material but can you give some examples or formulas to calculate it ? The best example would be the average speed of the air molecules (all types in ...
1
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1answer
39 views

How does acceleration affect the orbit?

I want to know what roughly happens if we hit an orbiting body a little. And how is it possible that most of the objects have seemingly circular orbits around. How do they stabilize? I ask because it ...
5
votes
4answers
427 views

How does the speed of electrons change around a circuit?

I have been thinking about ways of teaching electronics and I'm wondering if the following is true... For starters, when we talk about voltage as energy per unit charge, is this energy manifest ...
1
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0answers
16 views

Rapids in a River

Can I expect to have bigger or smaller rapids in a river that has a water level that is higher than average? I am not sure which way this would go. With the lower water, one is closer to the rocks, ...
1
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0answers
32 views

Speed of Water in a River

Does a river flow faster the higher the water level - or does it go at exactly the same speed? I was recently tubing in a river and the water seemed to be going faster with the water level being ...
3
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3answers
1k views

Why does the speed of the propellant limit the speed of a space ship in open space?

Isn't speed a relative thing in space? If so, why would the speed of a propellant matter? Why can't a space ship accelerate infinitely?
2
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0answers
63 views

-Thought Experiment- At superluminal speeds, to what degree would vision be impaired? [closed]

I was thinking about superluminal travel when thinking about advanced civilisations in the future. I was also thinking about the Doppler effect; so I decided to think about how light may be affected ...
0
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1answer
45 views

Helicopter wings

Why do the propellers on helicopter appear to be so slow when the propellers is going at full speed? Can you please explain this particular optical illusion to me?
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3answers
39 views

Kinematics - Concept of average velocity

Average velocity, as I have heard, cannot be found simply by finding the average of two numbers. I have a question on average velocity, but am simply unable to proceed: A particle moving in a ...
0
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1answer
51 views

Effects of gravity on light [duplicate]

If gravity can bend light, why can't gravity slow light. At least momentarily? Wouldn't that give the illusion of the universe expansion speeding up?
2
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3answers
70 views

Photon speed going from $0$ to $c$ initially? [duplicate]

I have read many questions which ask whether there can be photons at speed other than the speed of light and all of them are answered no! But when the photon is created for ex during electron ...
1
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1answer
19 views

Speed distribution in 1 dimension

In 3D, the maxwell velocity distribution is: $$f = \left(\frac{\alpha}{\pi} \right)^{\frac{3}{2}} e^{-\alpha v^2} d^3 \vec v$$ To get the speed distribution in 3D, we simply expand $d^3\vec v = 4\pi ...
0
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5answers
197 views

The speed limit is with respect to what?

As I understand, an object with mass cannot reach the speed of light because its (relativistic) mass increases "exponentially" as it approaches light speed. So there is a relation between mass and ...
2
votes
2answers
109 views

kinetic and potential energy

I have 2 cubes where one mass is greater than the other. $M$ and $m$, where $M>m$, and there is a hill that is symmetrical on both sides, and has a friction factor of $k$ between the object and the ...
0
votes
1answer
62 views

How to convert acceleration in g to speed velocity in meter /s [closed]

I'm working on an inertial measurement unit with some MEM'S component. I want to retrieve data on a micro-controller. I have 3-axis accelerometer sensor. however I want retrieve data in $mg$ ( ...
0
votes
3answers
77 views

Geostationary orbit and rotation speed of a planet

Assume for planets similar to Earth but with different rotation speeds (including zero), and we put a satellites at altitude of 35 786 km/hr (similar to the Geostationary orbit or earth), with speed ...
1
vote
2answers
141 views

Is there an equation to calculate the average speed of liquid molecules?

I seem to remember from first year physics that we can calculate the RMS speed of a stationary, ideal gas with $v=\sqrt{\frac{3RT}{M}}$. Does a similar equation exist for liquids?
2
votes
1answer
101 views

When photons are emitted, do they accelerate to reach the speed of light? [duplicate]

Photons are considered mass-less particle with a specific velocity but according to the electromagnetic theory, a photon is considered to have both energy and momentum. So what happen when they are ...
0
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1answer
62 views

Distance travelled given velocity at various moments of time [closed]

I am trying to solve a problem where I need to find the distance travelled at the end of the nth second and my input data contains only velocities at different time instances. Say for instance I ...
0
votes
1answer
57 views

Is there any significance to the negative sign on this speed?

A girl is riding a bicycle along a straight road at constant speed, and passes a friend standing at a bus stop (event #$1$). At a time of $60$ s later the friend catches a bus (event #$2$) If the ...
1
vote
1answer
71 views

Calculate speed of proton at infinity [closed]

I have this problem to solve: Two protons are on the x axis at x=-1 and x=0. An alpha particle is placed at x=2, and the proton on the left is released, find its speed at infinity. I know that this ...
1
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2answers
218 views

Position dependent speed, how to compute position

I can't solve a problem: $ A= 0.5 (ms)^{-1}$, $ x_0 = 0.5 m $, $v(t)= A \cdot x^2 $, I have to compute the position at $t=3$ ($x_0$ is the initial position). So my guess is that I should be able ...
1
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1answer
48 views

Spinning theoretical object moving faster than the speed of light [duplicate]

Let's say you have the Earth, or any celestial body, spinning as it is. What if you build a tower from the surface, and extended it out into space. If it was built far enough, could the furthest end ...
2
votes
2answers
143 views

Shouldn't the Uncertainty Principle be intuitively obvious, at least when talking about the position and momentum of an object?

Please forgive me if I'm wrong, as I have no formal physics training (apart from some in high school and personal reading), but there's something about Heisenberg's Uncertainty Principle that strikes ...
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votes
1answer
62 views

Finding the constant of gravity in a game [closed]

Minecraft is a game of mining where one digs and finds ore (to put it simply). the world is composed of "blocks" 3 dimensional cubes that have different "pictures" on them, that make them appear like ...
1
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1answer
45 views

Ultra Deep Field 3D camera speed

I guess most of you saw Ultra Deep Field 3D video. In the end it shows camera moving in 3D perspective through all the galaxies. My question is, how fast is the camera moving in that video? I couldn't ...
0
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1answer
36 views

Drift speed of electrons when the object is grounded

So I know that the drift speed of electrons is usually pretty slow. Let's say I have a charged sphere and I would ground it over a wire. How fast would the electrons leave the sphere? Would that drift ...
38
votes
7answers
3k views

Is it fair to judge this speedskating race by only 3 thousands of a second?

I'm reading this article: Zbigniew Brodka of Poland won the Olympic men's 1,500 meters speed skating title by just 0.003 seconds at the Adler Arena on Saturday. Brodka clocked one minute, ...
29
votes
3answers
3k views

Speed of sound at temperatures below 0 °C

How can the speed of sound be calculated for temperatures below 0 °C (down to -40 °C)? Does the calculation $v=331\ \frac{m}{s} + 0.6 \frac{m}{s°C} \times T$ still hold (where T's unit is ...
-2
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1answer
53 views

Displacement inside the moving Object

Suppose say a person is standing over the moving bike and he jumps while bike is moving, bike will move forward & person will land in same point at which he jumped, relative to earth position ...
0
votes
1answer
284 views

Distinguish between instantaneous speed and instantaneous velocity

I encountered a line in my text book of physics that: Average speed over a finite interval of time is greater or equal to the magnitude of the average velocity. But instantaneous speed at an ...
-4
votes
1answer
80 views

From where we can view earth moving?

Earth moves with a speed around $100000 \,\,km/h$, which will be amazing, but from where we can see that moving speed? If we far away from earth (outside of earth gravity) then can view its moving? is ...
5
votes
3answers
278 views

Why does a “speed of sound” exist?

I've recently read that wind cannot be faster than the speed of sound (german source). But why is there a speed of sound? I understand (well, mostly accept to be honest) that the speed of light in ...
0
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0answers
73 views

Light bodies at high speeds behave like heavy objects when recorded by a high speed camera

This is potentially a very dumb question, but recently I was looking at some slow motion footage of bullets hitting stuff and I realized something interesting. One of the clips showed two metal ...
0
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1answer
44 views

How is the universe is experienced at light speed? [duplicate]

When moving faster, we experience time dilation and space contraction. We often state that a photon does not travel through time, i.e. if it where capable of observation, it would not experience time. ...
1
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4answers
295 views

Calculate average speed with unknown variable accelaration

I am in the middle of a vehicle tracking project where I have to calculate the distance traveled by the vehicle in a given amount of time. Data I am getting: ...
1
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3answers
366 views

Relationship between power and max. speed

I'm talking about the maximum speed if let's say I have a car with the power $P = 1000 \text{W}$ and a force of friction of $5 \mbox{N}$ acting in the opposite direction. After some googling I found ...
-2
votes
1answer
57 views

What distance has the soldier travelled? [closed]

A troop $5$ meters long starts marching. A soldier at the end of the file steps out and starts marching forward at a higher speed. On reaching the head of the column, he immediately turns around ...
2
votes
2answers
357 views

What does it mean to be stationary?

I'm looking for a simple answer. What do we regard a stationary. Do we mean an object that is not moving noticeable from the viewers perspective because then a parked car would be considered ...
3
votes
1answer
378 views

How to Calculate temperature, given speed of sound and relative humidity?

I know the solution in reverse direction, but I find it very complex to go the other way around and calculate the temperature when given the speed of sound and relative humidity, any ideas?
5
votes
2answers
236 views

Is there a limit to frames per second to be captured?

Today we see ~100,000 fps cameras for hyper slo-mo. Is there a physical limit for frames per second for a camera? Speed of light maybe? How?
4
votes
2answers
186 views

Gravitation not instantaneous = non elliptic orbits?

When I studied physics some time ago my teacher explained that if we consider the gravitational atraction not instantaneous, such as the General Relativity says, the planets would be attracted towards ...
-2
votes
1answer
104 views

How Was the Speed of Light Discovered? [closed]

The title pretty much says everything; I just want to know how the speed of light was discovered.
2
votes
4answers
256 views

Is there an upper limit on the radius of a rotating wheel?

Is there an upper limit on the radius of a real wheel which is rotating at an Angular frequency of $\,\omega \,$ along its axis, such that we just require a finite amount of energy to rotate it? ...
0
votes
1answer
61 views

Speed Distribution [closed]

I came across a problem which reads: The speed distribution function of a group of N particles is given by: $dN_v = kv\; dv\; (V>v>0)$ $dN_v = 0 \; (v>V) $ (a) Draw ...
1
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1answer
49 views

Does speed of writing data on an optical disk affect the speed of reading data? [closed]

Does speed of writing data on an optical disk ( like DVD ) affect the speed of reading data from that disk ? even a little?
-2
votes
1answer
453 views

Average speed question [closed]

Find your average speed if you go 15m/s for 1000 m and then 30m/s for 1000 m I understand that average speed is total distance / total time. The distance for this problem would be 2000m travelled. ...
-2
votes
1answer
156 views

Calculation of 12000 Lunar Orbits/Earth Day [closed]

I am really interested in the calculation of the following speed value in meter-per-second unit: Speed of something that is able to travel in one earth day the distance that it would take for the ...
0
votes
1answer
737 views

Gentle slope vs steep slope

Take for example a slide of 3m tall. Would an object (starting from rest) sliding down a gentle slope have a lower speed than a steep slope? (Note: Height of slide is the same,disregard friction.) ...