Questions tagged [speed]
Scalar quantity which is the magnitude of velocity.
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How do i calculate the speed of the ball? [on hold]
A spring pushes a ball with 10 m/s on this bent track. What is the formula to calculate the speed of the ball in point A and point B. The track is horizontal so there is no g-force and the track has a ...
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Affect of walking upto and beyond lightspeed [on hold]
Setup: a giant planet rotating at the speed of light(L) + 1m/s at its equator (E)
Assume at E ± 1m the speed of rotation is L
Also, at both the South and North Pole the rotation is 0m/s such that ...
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1answer
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Water speed and reach of a water jet cutter
I Want to build a water gun that throws water 100 meter far under 1 second. is it possible? how can i build it? (please send the formulas if you can)
IF A water jet has 4mm nozzle and the pressure on ...
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2answers
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Velocity of a ball rebounding off a moving train
At the bottom of this page says (my emphasis):
It's interesting to note the speeds in the cartoon. The
propeller-beanie kid sees his tennis ball moving away from him at 30
miles per hour. So ...
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0answers
47 views
Wind energy as a function of speed and temperature
My fellow windsurfers, most of whom have little knowledge of Physics, all agree that the force of the wind when sailing in the Northeast of Brazil, where the weather is warm, is much less than where ...
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3answers
68 views
Do electric charges in an electric field move at a constant speed?
The electric field is given by: $$\vec{E} = \frac{1}{q}\vec{F}$$
Electric charges create an electric field which, in turn, creates a force that accelerates charges.
The Ohm's law, however, tells us ...
1
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1answer
34 views
Air velocity from a 5mm pipe
At first, I will try to describe my problem.
I have a compressed air at 0.4 MPa (4 bars) that goes trough a control valve and a flow meter into two 5 mm pipes.
Flow meter shows the value of 200 ...
1
vote
3answers
67 views
Find velocity from acceleration equation [closed]
Suppose the acceleration of a particle is a function of $x$, where
$$a(x) = (2.2 s^{-2})x$$
(a) If the velocity is zero when x = 1.0 m, what is the speed when x = 3.4 m?
(b) How long does it take ...
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0answers
40 views
How to beat speed of light using graphene pulley motor? [duplicate]
A 10 meter graphene pulley with 10,000 teeth, attached to a second graphene pulley of 10mm with 10 teeth both in a low temperature vacuum chamber.
The first graphene pulley is being rotated by a ...
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0answers
24 views
Relative speed of sound (relativistic velocities)
This question is about waves speed, not about waves frequency shift (I already know about Doppler's effect).
I know that for all the mechanical waves, e.g. sound, the perceived wave speed depends on ...
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0answers
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force by an air particle when hitting another air particle
I just had this really weird question.
On average, how much energy is lost, when one air molecules hits another air molecule?
By air molecule I mean one molecule of the gases in the atmosphere. On ...
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3answers
66 views
Can we accelerate a particle to a very high speed by applying force just once?
Suppose you have a tennis ball in your hand. When one would throw it towards a wall such that it encounter the surface of the wall at almost a right angle, the ball would come back in the same ...
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1answer
53 views
Does changing mass change projectile speed? [closed]
If a projectile is fires from a pistol with 10g mass, and somehow during flight it's mass is increased to 1000g, how does this affect it's projectile speed? (This is a DnD hypothetical question).
I ...
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4answers
118 views
Sound frequencies travel at the same speed?
as the diagram shows
sound frequencies travel at the same speed
or each frequency has a given speed
?
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1answer
58 views
How to calculate speed of shrapnel based on explosive's speed of detonation?
I'm trying to calculate the initial speed of shrapnel from a grenade.
Using the US's M67 hand grenade as a baseline/reference:
Total mass: 400g
Explosive's mass: 180g
Explosive's detonation speed: ...
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0answers
48 views
Why are velocity and kinetic energy not proportional? [duplicate]
In the equation $E_k=\frac12mv^2$ the fact that the kinetic energy of a moving object is not proportional to it's velocity seems counter-intuitive to me.
Put another way, it seems intuitive to me ...
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1answer
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Can I derive the 1 dimensional Maxwell-Boltzmann Distribution using this method?
I am aware that the 1D MB Distribution is usually derived by counting the momentum states in various directions. However, I would like to know if the following method using the 3 dimensional speed ...
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3answers
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Why do we need concept of average velocity and average speed? [closed]
As I was thinking about average speed / velocity, I got curious, why do we need this concept. This average speed / velocity doesn't give accurate information about motion of an object then why it is ...
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4answers
117 views
Why was the concept of velocity created? [closed]
Why do we use velocity instead of speed for different physics problems?
I recognize how they are different but why use one over the other?
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3answers
115 views
How fast does an electron move?
I've been reading this website: www.physics.wayne.edu/~apetrov/PHY2140/Lecture8.pdf to learn how fast an electron moves in a circuit.
On page #8, #9 and #10 It says to take the Cross-sectional Area ...
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0answers
34 views
Speed between two cars with radar
I found a programming problem that calculated the speed between two cars as below and I would like to know how the calculation is done. It is about determining the speed of lead car. The coordinate ...
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3answers
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How to calculate car engine acceleration and deceleration?
I'm trying to program some kind of car game in unity just for practice. So I want to start off with an engine that behaves normally, so I can then convert the engine's RPM into torque.
Currently, I ...
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0answers
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How to increasing the swing frequency/speed of pendulum with hollow sphere enclosing small solid sphere?
When a small solid sphere is enclosed inside a hollow sphere, for a pendulum. How it will change the swinging nature of the pendulum? How can we increase the swinging frequency/speed of the pendulum?
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High speed and low speed photons (hypothesis - difference/relation)
In this question I found an interesting answer with the source.
Quotation:
A telescope viewing a supernova from over 16 billion light years away
recently clocked the low energy photon arriving 5-...
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2answers
57 views
What is the exact mechanism of flow of electricity?
When a steady current
flows through a conductor, the electrons in it move with a certain average ‘drift speed’.
One can calculate this drift speed of electrons for a typical copper wire carrying a
...
3
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4answers
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What is the difference between uniform velocity and constant velocity? [closed]
I think that uniform velocity implies constant speed but not constant direction. while constant velocity implies constant speed without any changes in direction.
Both tell us that there's no ...
0
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1answer
27 views
Avarage Speed conventional formula VS Mean Value of Multiple Speeds [closed]
Here the basic problem:
The motion of an extraordinarily jubilant bird flying straight up and down is given by the graph below, which shows the vertical position y as a function of time t.
What was ...
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3answers
47 views
Why Didn't the Energy-Momentum Relation Work?
I am currently studying for the GRE Physics subject test by working through published past tests. My question is about problem 20 from the test GR8677:
A positive kaon ($K^{{}+{}}$) has a rest ...
2
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2answers
46 views
How can speed at a given position be estimated from a bunch of average speed measures at different positions?
I have loose measures of average speed in different positions (speed is in the x axis given particularities of my own problem)
How can I estimate a fitting curve for 'instantaneous speed at each ...
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1answer
79 views
Is it true that if one stood on Westminster Bridge with a radio, one would hear the chimes of Big Ben via the radio sooner than in the real world?
I was reading this review of Damon Krukowski’s Ways of Hearing in The Spectator when I stumbled across this claim:
“And before the renovation of Big Ben began, if you stood on Westminster Bridge ...
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0answers
46 views
How can the velocity of electrons in graphene be measured?
I'm trying to understand how one can measure the velocity of electrons in graphene, from an experimental point of view.
Does anyone have some clue?
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9answers
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The instant an accelerating object has zero speed, is it speeding up, slowing down, or neither?
This problem is from Khan Academy. Specifically for the blue point circled in red, the answer is that at this blue point, the object is neither speeding up nor slowing down. When I think about the ...
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1answer
28 views
Force measurement [closed]
We have a bike and a biker on it of mass 81 kg combined. Biker can reach speed around 30k/h.
And the question is: how to measure the force (in Newtons) applied on the bike to reach that speed in 10 ...
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1answer
70 views
Is there an intrinsic speed of time? [closed]
If time and speed is relative, then we could double the speed of every particle in the universe, as this increases the clocks rate we shouldnt be able to tell any difference.
But my question is, in ...
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0answers
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True Airspeed from Indicated Airspeed, Temperature, and Altitude
I'm working on an aircraft problem to figure out the true heading we need to fly in order to end up where we want with the presence of wind, and I think I have the whole thing figured out except for ...
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1answer
40 views
Scale diagram confusion
I’m familiar with scale diagrams where three forces act upon an object and trigonometry is used to find the resultant force, but I’ve come across questions that use units of velocity instead of force. ...
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7answers
110 views
Is there centripetal acceleration with velocity of 5 m/s?
So if an object is moving at $5\ \mathrm{m\ s^{-1}}$ in a circle, is it accelerating?
Me and a friend are having a conversation about this.
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0answers
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How does different shuffleboard powder affect the disks' speed
I do know there is friction and surface tension involved here but am not sure on how exactly does different kinds of shuffleboard powder affect the disks' speed.
So taking into the account the ...
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2answers
53 views
Speed and tangential acceleration in pendulum motion
Speed is a scalar quantity which corresponds to the magnitude of velocity, so it must always be nonnegative.
In a general 2d motion, the tangential component of acceleration is given by the time ...
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1answer
28 views
Would not the oscillation of light slow down the wave? [duplicate]
Would not the oscillation of the light wave slow down the wave? Does light travel at "c" of its net position over time, or does it travel at "c" on the wave?
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1answer
76 views
Meaning of REALLY Slow Speeds
So we have a fairly good grasp of how entities behave at extremely fast speeds (visa vi relativity etc) but what about incredibly slow speeds?
I’m a Physics student and we were covering Broglie waves....
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0answers
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How is vectorial Doppler computed when both transmitter and receiver are moving?
In a technical document, I have found the following formula for the Doppler of two moving devices:
$d=\frac{\bar{r}_{rx}^T\cdot \bar{v}_{rx}+\bar{r}_{tx}^T\cdot \bar{v}_{tx}+2\cdot \alpha\cdot D}{\...
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1answer
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Does Horizontal Velocity remain constant when it hits a surface in a Parabolic Motion?
It is told in one of the answers that the horizontal velocity stays at 4.0 m/s after the ball bounces from the plate.
Why is it still at 4.0m/s, isn't there friction or is it neglected for the sake ...
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2answers
3k views
If a black hole is created from light, can this black hole then move at the speed of light?
Imagine we managed to squeeze light into a very tiny region of space so that the energy concentration at that point becomes a black hole. Can this black hole then move at the speed of light?
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3answers
109 views
What is the best way to conceptualise a 'division' [closed]
This may seem like a strange question, but my question is more along the lines of trying to figure out how people were able to 'discover' the formulas which have shaped our understanding of the ...
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0answers
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How to express the Earth's orbital speed as a function of time?
I would like to create a function that tells me the orbital speed of Earth at any given day. The vis-viva equation says that
v=√(GM(2/r-1/a) ), expressing speed as a function of distance from the ...
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3answers
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If you were to push a block in space in an ideal vacuum scenario with zero friction, what would be the final velocity of that object
Say you push an object with 10 N force(just once and let it go) of mass 10kg object in space with zero friction and nothing in the way of its path. What would be the velocity of that object?
I would ...
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1answer
91 views
Calculate speed of an object using angle and time [closed]
I haven't had any physics class or anything close to that in a long time, and I'm currently confronted with an exercise I don't remember the formula(s) to solve it.
Assuming I have an object of ...
0
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1answer
109 views
Is it speed or acceleration that leads to time dilation? [duplicate]
Is it acceleration or speed that leads to time dilation or both?
For example, when a spaceship accelerated to (almost) the speed of light, then reversed course to come back towards earth, does this ...
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votes
1answer
105 views
Can a projectile bullet kill? [closed]
Today, I was watching a movie, in which a person shot a gun in air. The bullet went high in sky, became stationary for a moment and dived back and killing a non-innocent person by hitting him in head ...
