Scalar quantity which is the magnitude of velocity.

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3
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2answers
267 views

Paradox while Cooling & Heating in Air? [duplicate]

I was thinking about how asteroids get "burned" up in the upper atmosphere as they approach the earth surface due to the atmosphere of earth heating the asteroids immensely as a result of air ...
1
vote
3answers
864 views

Does the speed at which sound travel depend on the volume (amplitude) of the sound?

Lets say you have a plank is you hit it once and get t time if you hit is 2x as hard will it travel t/2? will it be the same or will it travel only slightly faster?
0
votes
0answers
29 views

What if there was a hole between earth poles [duplicate]

Imagine if there was a hole between two earth poles, let's say 100 meters wide, as deep as the Earth's height between north and south poles - what would happen if we threw an object from the North ...
6
votes
2answers
354 views

Speed of sound in gaseous medium

Why does the speed of sound decrease as the density of the medium increases? I know why this happens mathematically, but I want to know what happens at the molecular level that results in higher speed ...
19
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9answers
10k views

Can a human size object move so fast that it ceases to be observable?

In many anime, comics, movies, etc, we see a lot of super human beings moving and fighting at such high speeds that a regular human being cannot see that they are fighting or moving pass by. In ...
0
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1answer
77 views

How can time-travel be possible if speed is relative? [duplicate]

I have heard that time-travel is possible...relative to some observer. So, as I understand it, the following example would be accurate: There are two twins- TwinA and TwinB. Both have very accurate ...
1
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1answer
62 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 ...
0
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1answer
1k 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 ...
3
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5answers
2k views

comparing torque and 0-60 speed in cars

Im looking a two cars, both are the same model but ones got a 2.0L turbo petrol engine and ones got a 3.0L turbo diesel engine. These are the full specs 2.0L Petrol 3.0L Diesel what im ...
0
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1answer
59 views

What happens when the speed of a body is less than optimum speed?

Yesterday I learned about optimum speed. My teacher told that optimum speed is the speed with which one can take turns on banked road without wear and tear. $v_0=\sqrt{rg\tan\theta} $, $v_0$= ...
2
votes
3answers
235 views

How fast can fire spread?

You can build a home-made flamethrower by using a spray and a lighter: (from this YouTube video) But this can be dangerous if the fire gets in the can and the can explodes. So I guess the speed at ...
0
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1answer
86 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 ...
-3
votes
3answers
353 views

How could we define speed without time?

This is a bit of a brain twister but it's a very serious question. Please be precise in your answer. I do not believe time exists. I believe it is simply an illusion of our perception, the ...
7
votes
2answers
608 views

Riddle about speed

This stems from a riddle I read in a magazine perhaps 20 years ago so I apologise for the imprecise recollection. A dog that can run infinitely fast is placed on an infinitely large flat surface and ...
1
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2answers
83 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 ...
1
vote
1answer
65 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 ...
4
votes
4answers
1k 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
vote
0answers
25 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
43 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 ...
0
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2answers
4k views

How to calculate fuel consumption of car (mpg) from speed and accleration knowing mass, drag coeff and rolling resistance?

How can I calculate the current (instantaneous) mpg of my car if I know the speed and acceleration of the car? From reading various answers for the "car going level or up/down hill" question asked ...
4
votes
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
votes
0answers
95 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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3answers
231 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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3answers
376 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 ...
0
votes
1answer
56 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
votes
3answers
111 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 ...
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4answers
541 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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1answer
394 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
253 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
149 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
460 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 $mg$ ( ...
2
votes
4answers
272 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
410 views

Angular velocity $\omega$ by $v$

We have two girls, with mass ($M$). They become close to each other in speed of $V$. The distance between them is $3L$. I was asked to calculate the Angular velocity ($\omega$) of the two girls. So ...
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2answers
1k 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
163 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
votes
1answer
299 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 ...
1
vote
1answer
230 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
vote
2answers
226 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 ...
11
votes
5answers
3k views

Why would a fat skydiver fall first in free fall?

I was having one of those obnoxious conversations with a friend where he was arguing that a fat skydiver would reach the ground faster than a skinny skydiver. To me it seemed as obvious that the world ...
1
vote
1answer
223 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
279 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 ...
3
votes
2answers
614 views

Origin of motion and relative speed of bodies in the universe

Charged particles can hit the earth at relativistic speeds. But it seems that all large bodies have fairly low relative speed. Of course, speed can increase considerably when a body orbits close to a ...
30
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 ...
-1
votes
1answer
94 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 ...
40
votes
7answers
4k 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, ...
1
vote
1answer
54 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 ...
2
votes
2answers
133 views

What are the consequences in high-energy of the non-interaction of the Higgs Field?

At high-energies when the Higgs field won't affect (interact with) particles, when the symmetry breaking won't occur, what would be $\rm W\pm$ or $\rm Z^{0}$ bosons speed if they would then have a $0$ ...
-1
votes
1answer
119 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 ...
1
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3answers
2k 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 ...
4
votes
2answers
250 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 ...