The velocity tag has no wiki summary.
3
votes
2answers
880 views
How to deduce the theorem of addition of velocities?
Lorentz contraction and time dilatation can be deduced without Lorentz transformation. Can you deduce also the theorem of addition of velocities
$$w~=~\dfrac{u+v}{1+uv/c^2}$$
without Lorentz ...
7
votes
9answers
6k views
Why does the mass of an object increase when its speed approaches that of light?
I'm reading Nano: The Essentials by T. Pradeep and I came upon this statement in the section explaining the basics of scanning electron microscopy.
However, the equation breaks down when the ...
6
votes
4answers
754 views
Double light speed
Let's say we have 2 participles facing each other and traveling at speed of light
Let's say I'm sitting on #1 participle so in my point of view #2 participle's speed is c+c=2c, double light speed? ...
8
votes
1answer
2k views
From how high could have Felix Baumgartner jumped without disintegrating like a shooting star?
Today Felix Baumgartner jumped from 39 kilometres high and reached the earth safely.
Just considering friction, from how high can a human jump?
I expect that from a certain height, he would have ...
5
votes
4answers
656 views
A Basic Question about Gravity, Inertia or Momentum or something along those lines
Why is it that if I'm sitting on a seat on a bus or train and its moving quite fast, I am able to throw something in the air and easily catch it? Why is it that I haven't moved 'past' the thing during ...
0
votes
2answers
465 views
What will be the relative speed of the fly? [duplicate]
It has happened many times and i have ignored it everytime.
Yesterday it happened again .
I was travelling in a train and saw a fly (insect) flying near my seat.
Train was running at a speed of ...
2
votes
4answers
292 views
Why are coordinates and velocities sufficient to completely determine the state and determine the subsequent motion of a mechanical system?
I am a Physics undergraduate, so provide references with your responses.
Landau & Lifshitz write in page one of their mechanics textbook:
If all the co-ordinates and velocities are ...
2
votes
4answers
545 views
How long must escape velocity be maintained?
Escape velocity from Earth's surface is 11.2 Kilometres/second
How long would one need to maintain this escape velocity to actually escape Earth's gravitational pull? Must this 11.2 km/s velocity ...
2
votes
2answers
1k views
Mass of particle near light speed in a medium
I am trying to get a common understanding from these two previous questions:
Why does the mass of an object increase when its speed approaches that of light?
What happens if light/particles exceeded ...
3
votes
2answers
593 views
Group Velocity and Phase Velocity of Matter Wave?
In quantum mechanics, what is the difference between group velocity and phase velocity of matter wave? How can it also be that phase velocity of matter wave always exceeds the speed of light?
2
votes
0answers
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2D Car Physics including Throttle
For a simulation for testing on automatic cruise control, I came across the equation:
$$
v_{n+1} = (1 - k_1 / m) v_n + (1 - k_b) \begin{pmatrix}
T_n \\
θ_n \\
\end{pmatrix}
$$
where:
$T$ = ...
1
vote
2answers
124 views
Functions of Time
1) Is position a function of time only or also velocity? Likewise, is velocity a function of time only or also the position?
2) The following are functions of time:
$s(t)$ = distance a particle ...
-4
votes
1answer
182 views
Tricky Conservation of Momentum problem: find the ratio of the carts by mass percentage lost [closed]
A wagon is coasting at a speed $v_A$ along a straight and level road. When 42.5% of the wagon's mass is thrown off the wagon, parallel to the ground and in the forward direction, the wagon is brought ...
2
votes
3answers
784 views
What is the velocity area method for estimating the flow of water?
Can anyone explain to me what the Velocity Area method for measuring river or water flow is?
My guess is that the product of the cross sectional area and the velocity of water flowing in a pipe is ...
11
votes
2answers
726 views
How fast would a spaceship have to go to reach Alpha Centauri within a person's lifetime?
Given the recent news about the discovery of an "Earthlike" planet orbiting Alpha Centauri (our nearest stellar neighbour) it got me wondering just how fast would spaceship have to travel to be able ...
5
votes
2answers
781 views
Escape Velocity of Asteriod 243 Ida
I was reading about this asteroid (apparently, it has a moon, isn't that awesome?) and I started thinking about if I was on this asteroid, and I jumped, would I fall off?
It's been a while since I ...
1
vote
2answers
497 views
Difference between deltaV and specific impulse
When reading any literature regarding space propulsion, I keep getting about these terms deltaV and ISP or specific impulse. I know specific impulse is supposed to be the velocity the propellant mass ...
0
votes
2answers
384 views
Does an airplane's speed include the speed of the Earth?
After take off, does airplane's speed include Earth's movement/speed? Do airplanes turn with Earth movement/rotation?
5
votes
2answers
253 views
Explanation that air drag is proportional to speed or square speed?
A falling object with no initial velocity with mass $m$ is influenced by a gravitational force $g$ and the drag (air resistance) which is proportional to the object's speed. By Newton´s laws this can ...
4
votes
2answers
2k views
Flow of liquid among branches
If water is flowing through big pipe is branched into 4 branches of small pipe. Lets say the flow is around 4 m/sec.
I have the following questions:
What will be the flow rate in each of the ...
3
votes
2answers
164 views
Air velocity in a double-skin facade
I was wondering how the air flows in a double skin facade? Say I have a glass facade with a depth of 1m, a height of 200m and a width of 10m. It is a single vertical shaft all the way up with openings ...
2
votes
3answers
251 views
Train crash: are these situations alike?
I was just wondering... I believe that if a car travelling 50 miles per hour crashes into a wall, the result should be the same as crashing to another car also travelling 50 miles per hour (but in the ...
2
votes
0answers
155 views
If you make a steel rod from here to Alpha Centauri and move it, will the movement appear there instantly? [duplicate]
Possible Duplicate:
Is it possible for information to be transmitted faster than light?
imagine this theoretical situation:
You have make an extremely long piece of steel (or anything ...
1
vote
4answers
213 views
Light traveling through a medium
Does the frequency of light change when it travels across an interface between two media? What happens to the light wavelength and the light velocity at the interface?
I've gotten different answers ...
1
vote
1answer
154 views
Connecting 4-velocity to equation for adding velocities
Is there a way to connect 4-velocity to equations for adding speeds? I know 4-velocity $U^\mu$ is derived like this:
\begin{equation}
\begin{split}
P^\mu &= m U^\mu \Longrightarrow
U^\mu = ...
