Scalar quantity which is the magnitude of velocity.

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2answers
2k views

Why does time slow down when traveling at high speeds [duplicate]

One of the effects of traveling at high speeds is slowing down of clocks. I can understand gravity time dilation effect but not how would velocity affect clock speeds. How correct it is, if I say ...
0
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0answers
43 views

How to determine speed/energy of something dropped from a given height?

Say I dropped a ball from some height, which is measurable, is it possible to determine the speed of the ball when it hits the ground and thus the force exerted on the ball my the ground (or vice ...
2
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0answers
61 views

What does it look when we travel at the speed of light? [closed]

Suppose we're in a spaceship or in a car which runs at the speed of light. We are watching the light which is coming towards eyes at the speed of the light. What would it look like when the driver ...
4
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5answers
2k views

Force required to drive car

From what I know of Newtonian Mechanics, if an object is moving at a constant velocity, the net force acting on that object is equal to zero. If there is friction, then the applied force required to ...
0
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2answers
256 views

Speed of electrons in resistors

What affects the speed of electrons in a resistor? If two resistors are connected in series, they both have the same current; same number of electrons passing at a point per second. Suppose one ...
2
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0answers
60 views

Force and Energy in robots

There are two similar and hypothetical robots that move with wheels powered by motors, Robot A and Robot B. Robot A has a gear ratio of 3:1 (The gear connected to the motor is three times larger than ...
1
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1answer
494 views

how does air pressure affect the speed of sound

How does air pressure affect the speed of sound in relation to its kinetic theory etc? I have tried searching this but i have not found a suitable answer as other websites simply related to air ...
0
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1answer
118 views

If we could not see, would we think that nothing can go faster than sound?

And if so, then why does everybody keep asserting nothing can go faster than light speed (I'm implicitly assuming there could be something which we do not observe, which goes faster than light)?
7
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8answers
1k views

How to know if a vehicle is moving without any external source of information?

The situation is the following: I'm inside a vehicle (plane or a car, it doesn't matter) and I need to know if the vehicle is moving at a constant speed BUT I cannot perceive any external change like ...
29
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9answers
4k views

What is the speed of the fastest moving body in our solar system?

On Wikipedia I saw that the average orbital speed of planet Earth around the Sun is a whopping $29 783\text{ m/s}$, and it made me wonder are there bodies (planets, meteorites, asteroids) that move ...
15
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5answers
6k views

How fast would someone have to run to travel vertically up a wall?

I am currently doing a physics project on the effects of so-called 'super-speed'. I was wondering how fast you would have to run to vertically travel up a wall? That is, to negate the force of ...
1
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1answer
84 views

Why seeing further in “timespace” does not add up?

I've read that astronomers have received a light (a photon) 13 billion years old. Here's my question: If we start to turn the clock backwards all matter, energy, etc should start heading to the ...
1
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1answer
109 views

Rotating metal sphere

My knowledge of physics is not that great, but I am always willing to learn. I have the following question: If we have a sphere made out of metal with a radius of 1 meter, and it rotates in an ...
1
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2answers
737 views

What causes an increase in sound speed in a medium?

Its an established fact that increase in the temperature causes increase in speed of sound waves but what is the property which is changed by changing temperature ? Does frequency and wavelength get ...
1
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2answers
169 views

What is the speed of an electric spark/arc in vacuum?

I am just curious about the nature of an electric spark, how fast are the electrons moving? Will these electrons slow down when the spark occurs through a dielectric? (e.g., air)
2
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1answer
65 views

General equation of a wave

My book says that functions which represent a wave motions satisfy the differential equation : $$ \frac{\partial^2 y} {\partial^2t} = v^2 \frac{\partial^2 y} {\partial^2x} $$ where $v$ is the ...
1
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1answer
609 views

How can I calculate the speed of an object knowing its horizontal and vertical velocity components?

Let's say a ball is thrown and it experiences typical projectile motion (moves in a parabolic arc etc.) and the only information we know are the equations for the horizontal and vertical components of ...
2
votes
1answer
205 views

How fast would a bullet travel through liquid air?

According to Wikipedia, a bullet from a .22 Long Rifle travels at a speed of 320 m/s and the density of liquid air is 870 kg/m3. What equation would calculate the speed of a bullet fired into liquid ...
2
votes
1answer
45 views

Acceleration format and interstellar units

Calculating with m/s$^2$ is very helpful when dealing with acceleration on the human range, as accelerating from rest at 4 m/s$^2$ for 3 seconds will give a velocity of 12 m/s. g is also a very ...
5
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2answers
209 views

Can a number of gravitational slingshot stop a planet?

The answers to Where does the extra kinetic energy come from in a gravitational slingshot? state that in a gravitational slingshot the object being accelerated "steal" speed from the planet (or moon). ...
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1answer
114 views

How do you find the average speed and average velocity? [closed]

The shuttle craft "Galileo" travels at a constant velocity of $2.73*10^3$ m/s up for $34.0$ min. and then turns around to travel $1.45*10^3$ m/s down for $15.0$ min. a) Find its average speed. b) ...
3
votes
2answers
264 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
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3answers
845 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
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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 ...
17
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4answers
4k views

Why is there a controversy on whether mass increases with speed?

Some people say that mass increases with speed, some people say that the mass of an object is independent of its speed. I understand how some (though not many) things in physics are a matter of ...
0
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1answer
72 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 ...
19
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9answers
9k 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 ...
8
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5answers
863 views

Is speed an intensive property?

I remember being taught in elementary physics that while it makes sense to add volumes, masses, or heat, it makes no sense to add temperatures. As I wanted to use that to illustate some other issue, ...
0
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1answer
58 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
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3answers
230 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 ...
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3answers
339 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 ...
6
votes
2answers
345 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 ...
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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 ...
2
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1answer
642 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
64 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
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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
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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
42 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 ...
4
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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
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 ...
1
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1answer
73 views

Helicopter blades

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?
0
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3answers
216 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
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
110 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
376 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
441 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
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3answers
355 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
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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?