Questions tagged [speed]
Scalar quantity which is the magnitude of velocity.
715
questions
0
votes
0answers
15 views
How to accumulate torque of multiple independent gears? [closed]
If I have 3 gears meshed with a gear in the center of the 3 gears as shown in the picture. all of those 3 gears are connected to different power sources. They are free to rotate in the same direction ...
0
votes
0answers
39 views
If traveling with relativistic speeds can observer find space denser than normal?
I know that outer space contains few particles per cubic meter, but I am curious if travelling that fast for our brave traveller all of these particles will look like a dense pool of molecules.
And ...
-2
votes
0answers
46 views
Straight Motion Kinematics Equation [closed]
Please explain to me, for the interval $15\leq t\leq 20$, why $x(t)=x(15)+8t=x(0)−160+8t$
with $v(t)=+8$, and the positive sign (+) indicates the direction to the right.
0
votes
0answers
45 views
Is mass relative? [duplicate]
Since time is relative to the observer's velocity, does that mean that velocities are also relative, since the same distance is covered in a different time, depending on your reference frame? If ...
0
votes
1answer
34 views
How to calculate the speeds two objects need to move at in order to reach different destinations at the same time [closed]
For example: On a graph there are two points. Each point has a different destination. The distance between Point A and its destination is 50, and the distance between Point B is 100. The points will ...
0
votes
1answer
36 views
Velocity while falling from table
Suppose there is a chain of mass $m$ in a semicircular tube of radius $r$. If it's pushed, then find the velocity of the chain while leaving the tube.
This is a simple problem which we can do using ...
0
votes
1answer
35 views
How does acceleration relate to the rate of change of speed?
I am given the following question:
The trajectory of a charged particle moving in a magnetic field is given by $\textbf{r}=b\cos(\beta t)\textbf{i}+b\sin(\beta t)\textbf{j}+ct\textbf{k}$ where $b,\...
0
votes
2answers
34 views
Maximum Rotation Speed
I looked at a question, elsewhere on this site, relating to the maximum 'theoretical' speed of rotation. The explanation using the speed on a black hole event horizon seemed reasonable to this person.
...
0
votes
2answers
69 views
Variables in rectilinear motion
I wrote a post few days earlier on circular motion but it seems i still haven't got the hang of it yet. When is this equation actually true?
$s=ut+\frac{1}{2}at^2$
Suppose velocity is given by $v=t-2$ ...
0
votes
1answer
37 views
Why is the speed of a distant object proportional to its distance from a reference object?
Why is the linear speed of a distant object in space proportional to its distance from a reference object (Earth in this case)? How can we derive this?
If I consider a sphere with volume expansion ...
0
votes
4answers
84 views
Velocity squared confusion
As far as I know, a vector cannot be squared. Velocity is also a vector, though we have equation of motion, $v^2=u^2+2aS$. I am perplexed with $v^2$ here. What does it imply?
14
votes
5answers
3k views
Can nothing other than light have speed independent of source?
Is it impossible for there to be some phenomenon that travels at a different speed than light to have speed independent of the source? Because if there were such a phenomenon there would be competing ...
5
votes
8answers
2k views
The faster you move, does it take more and more energy to increase your speed at the same rate?
I'd like to confirm this somewhat counterintuitive result. Starting with the definition of kinetic energy:
$$E = \frac{1}{2} mv^2$$
Assume a vacuum, no external forces, and starting from rest. Adding ...
0
votes
0answers
26 views
Is two cars colliding at 100 km/h the same as one car colliding into a wall? [duplicate]
Two identical cars collide head-on. Each car is traveling at 100 km/h. The impact force on each car is the same as hitting a solid wall at what speed?
I have tried solving it but I don't understand ...
2
votes
2answers
57 views
Finding average speed of a body traveling between two points [duplicate]
A body travels from A to B at 40 m/s and from B to A at 60 m/s. Calculate the average speed.
Can't we just add the given speeds and divide by 2 to get the average speed? This way answer would be 50 m/...
1
vote
2answers
47 views
At what speed does wind generate warming of an object due to drag, making the object warmer than the ambient temperature?
At what speed does wind generate warming of an object? Say I'm outside at 0°F. How fast does the wind have to be to raise my exposed skin temperature to 40°F? Would that wind speed be so high it would ...
0
votes
1answer
34 views
9
votes
4answers
1k views
Can massless particles travel slower than the speed of light in vacuum?
We know an object with positive mass cannot be accelerated to the speed of light because this would require an infinite amount of energy. My question is:
Is there anything in the universe that can ...
0
votes
3answers
90 views
Is there any explanation from special relativity regarding the speed of a fly inside a car?
I have faced a scenario mentioned in this Question.
There was a fly inside my car and I was travelling so fast. shutters are opened in the car. I observe that when I slow down and accelerate, there ...
0
votes
2answers
80 views
Is it possible to calculate bike needed leaning angle from steering angle?
For a bike steering with radius of curvature $r$, we have
$$\theta = \arctan \frac{v^2}{gr}$$
but you need to know r. I want to calculate the leaning angle from steering angle. It should be just ...
0
votes
2answers
49 views
How to calculate optimal bend angle for moving monowheel vehicle?
Imagine you are driving a monowheel vehicle (https://www.google.com/search?q=monowheel) at some speed S (km/h) and you need to take a curve, so you steer by angle A in the respective direction, BUT to ...
0
votes
2answers
24 views
Is it possible to derive a distance time graph from a displacement time graph?
If I take the derivative of a displacement-time function, it will give the function of its velocity over time. If I take the absolute value of my velocity function it will give me a function of its ...
0
votes
0answers
14 views
Mass of a free falling object [duplicate]
What does General Theory say about the mass change of a freely falling object in a gravitational field? That is, does its mass change as the velocity increases? And, similarly, does the mass of an ...
-2
votes
3answers
48 views
Does horizontal motion decrease with the increase in gravity?
If a ball moves horizontally with a constant velocity in Earth compared to a ball moving with the same velocity but in a thicker gravitational field, will the ball move slower in the other plane ...
-1
votes
1answer
52 views
What is the speed of this spaceship? (Relativity) [closed]
There is a spaceship that located in Alpha Centauri (let's say spaceship A) and there is another spaceship located in Solar System (spaceship B).
If:
A is moving away from Alpha Centauri and Solar ...
0
votes
1answer
48 views
Would a simple experiment show that pressure transmits through water at the speed of sound?
Let say we have a 100 m long metal pipe with its two ends equally positioned at 1 m above the rest of the pipe. The ideal case would be a U-shaped pipe... The pipe is whole filled with water. Now, if ...
0
votes
1answer
36 views
Dispersion / group velocity in tapered fiber
dispersion in fibers are defined as:
$$D=-\frac{2 \pi c}{\lambda^2}\ddot{\beta}$$
where:
$$\ddot{\beta}=-\frac{1}{v_g^2}\frac{dv_g}{d\omega}$$
where $v_g$ is group velocity
Does the group velocity / ...
1
vote
2answers
57 views
Is it possible to tell the speed of Shoaib Akhtar's hand after delivering the fastest ball?
Fastest bowling in cricket history is Shoaib Akhtar's 161.3 km/h.
From Google.
Then what was the speed of his arm when he delivered the cricket ball to the pitch? Is it possible to tell? Hand cannot ...
1
vote
2answers
184 views
If lower gear generates more torque at the wheel, why does it generate less acceleration/speed of the car compared to higher gear?
If lower gear generates more torque (compared to higher gear) at the wheel, that would presumably mean the wheels can exert more force on the floor to propel the car forward. Thus, why does lower gear ...
0
votes
1answer
35 views
Determine speed of moving vehicle from video taken in a moving vehicle [closed]
I have dash camera footage from my motorcycle where the police were speeding illegally in dangerous conditions. I know my speedo is 7% over so if it reads 107KPH a radar gun will ping me at 100KPH.
I ...
0
votes
1answer
30 views
Speed of sound in a solid calculated theoretically
I am trying to find theoretically precise values of the speed of sound in various solid materials. I have found the CRC Handbook of Chemistry and Physics with a table of values with no uncertainties ...
0
votes
1answer
50 views
What is the velocity of ant? [closed]
My Approach:For any arbitrary motion of A and B, C must move in such a way that it forms a new equilateral triangle A'B'C'. Now how do I derive a relation between their displacement vectors so as to ...
2
votes
0answers
11 views
Venturi Effect?
I was rinsing out my recyclables when it seemed to me that a 24 oz. plastic bottle drained A LOT faster than a 12 oz. can when held upside down. So I tried it again and sure enough the 24 oz. bottle ...
0
votes
1answer
27 views
Local speed of sound in a perfect gas
I have some doubts regarding the derivation of the formula for the local speed of sound in a perfect gas. I am going to use the related wikipedia page as a blueprint to expose my doubts.
We can show ...
1
vote
0answers
22 views
What happens to a Maxwell-Boltzmann speed distribution when samples mix?
I have a few questions related to how it changes when two samples mix.
How would it change if two identical samples, one with higher KEavg and one with lower KEavg are added together? would the peak ...
0
votes
1answer
53 views
What if speed of air exceeds 340m/s?
We know that Mach cones are formed when an object moves faster than the speed of sound. This creates huge noise in the surroundings.
Here the airplane is moving faster than sound relative to ...
0
votes
0answers
15 views
How loud would a sonic boom that occurs at 60,000 (and 85,000 and 35,000) ft altitude be to observers at sea level?
I am aware that breaking the sound barrier over the U.S. is currently outlawed, as detailed by this release. So, I was wondering how big of a deal the sonic boom of aircraft would be to those on the ...
0
votes
3answers
50 views
Where does speed and velocity differ? [duplicate]
I'm in Junior High and I still have some confusion towards speed and velocity. They sound like the same thing, where some object moves in a given direction, but there is a difference from both topics.
...
1
vote
1answer
37 views
The speed of a particle when instead of pure circular motion it is forced to do a helicoidal-circular motion [closed]
Is it right that if a proton is trapped in a magnetic field it is forced to do a circular motion of a distinct radius.Now, if a quark inside that proton does a rotation inside the proton volume can ...
0
votes
1answer
46 views
How does Air Resistance affect the motion of a plane?
I am learning basics of physics, I have a doubt regarding air resistance.
Plane 1 and Plane 2 have same mass and surface area.
If plane 1 starts its flight by applying 500N force (numbers are rough ...
2
votes
1answer
109 views
Rotational motion from curved slope?
So I've learned for any slope with a sliding object, say a box, the speed at the bottom only depends on the height it was dropped from because of conservation of energy, assuming absence of friction ...
2
votes
0answers
23 views
Finding how to calculate the speed of a magnetic train through a coil in a simple DIY Hyperloop model
before I start, let me just say that I am terrible at physics, and this question might have some inaccurate vocabulary. I apologize for that.
I am currently working on a physics model (both ...
1
vote
1answer
46 views
Why is air resistance so counterintuitive?
By forming the ratio of the drag to weight, you find that it is exactly proportional to the ratio of the velocity to the terminal velocity. This gives the result that linear drag is negligible for ...
2
votes
1answer
27 views
Average speed and RMS speed, given speeds of objects
I am given the speeds of eight objects, and I have to find the average speed and the RMS speed of these objects.
I tried taking the actual average of these speeds: $\frac{1}{8}\Sigma(v_i)$, but I get $...
0
votes
1answer
39 views
How can mean free path affect the propagation of sound in a gas?
I was thinking, since mean free path is a measure of "how long" a particle has to travel to collide with another, that this surely must influence sound propagation somehow. I would say this ...
11
votes
6answers
1k views
Can relativistic mass actually change gravitational pull?
I've heard that relativistic mass can influence gravity, but this seems to create a paradox, unless I am missing something.
It seems to me that if there were two celestial bodies that are observed to ...
0
votes
0answers
19 views
Visualisation tool for different speeds? [duplicate]
I'm a student often doing kinematics word problems with objects moving at X km/h, Y m/s, or Z cm/s. Yet, I have no idea what these units look like in real life.
Out of curiosity, I'm searching for a ...
0
votes
1answer
110 views
Conversion between pressure in PSI and velocity [duplicate]
My question is about whether you can convert the pressure something has to the velocity it will have. For example, if I had water shooting out of a hose at 100PSI, could I calculate the speed that the ...
0
votes
1answer
48 views
In a sine wave, what is the minimum possible distance between two particles which always have the same speed?
I was going through my book when I came across this statement which was stated as a fact.
'That the minimum distance between two particles always having the same speed is $\frac{\lambda}{2}$ where $\...
0
votes
1answer
25 views
Why is the speed of propagation of electrostatic force indifferent from the type of media?
Let say we have a charged sphere and a reactive material 1m away.If we introduce a media between them that attenuate the speed of the electrostatic force we should clearly see that the reacting ...