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Questions tagged [velocity]

The time rate of change of the position of an object

4
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2answers
72 views

There are two velocities on the sphere. How to sum them on the sphere?

As shown in the figure, there are two velocities on the sphere, one is the velocity along the meridian direction, the arc length is its size, the other is the velocity along the equatorial direction, ...
-2
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0answers
33 views

Rain Car problem [on hold]

Rain falls with a speed of $10√2$ m/s. It makes 45° with vertical and 45° with a line drawn towards the north. Find the velocity with which car has to travel in the east direction so that for a person ...
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0answers
21 views

Find the deceleration of a car during braking [on hold]

the question is: How do you find the deceleration of a car during braking, if you only know the stopping distance of 35.6m at 100km/h??
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2answers
57 views

What's meaning of velocity of electron?

How do we define velocity of microscopic particles at small scales. As for macroscopic particle we can scale the distance travelled by object. But this is not the case with electron. Still, while ...
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0answers
29 views

Independence of position and velocity vector [duplicate]

Hi I am a mathematics student with an interest in Physics. In our Physics elective our prof. said if $\vec r$ denotes the position vector then the velocity vector $\vec v = \vec {\dot r} $ is ...
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1answer
37 views

Hyperbolic motion with non-zero initial velocity

The equations of hyperbolic motion in a single spatial direction with initial velocity of zero are pretty easy to find given a bit of googling, such as in this answer. And while I'm too rusty at ...
0
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1answer
37 views

Rapidity in 4-vector Transformation

In Lorentz transformation we have a concept of rapidity as related to boost. Rapidity is defined as a hyperbolic angle α such that $$\tanh(α)=v/c .$$ This further defines a matrix for Lorentz ...
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0answers
23 views

Vertically move in a helicopter to go somewhere on Earth [duplicate]

Is it possible to go from point A to point B (which are on same latitude) by hovering above A and wait till the earth rotates to point B below and then come down vertically? I believe there would be ...
3
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2answers
96 views

How to decelerate from velocity $v$ to stop time $t$ over distance $d$? [closed]

I'd be grateful for some help with this problem I am trying to solve. Let's say that I have an object travelling at a velocity $v$. I want that object to come to a halt in time $t$ AND travel exactly ...
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2answers
33 views

Speed is different when differentiating a function and when not differentiating

I have the function, $S(t) = t^2$. When Finding speed $= V = \frac{dS}{dt}$, we get $V = 2t$. Now If, I don't differentiate it and simply put $V = \frac{Distance(S)}{Time(t)} = \frac{t^2}{t}$ We ...
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3answers
73 views

Confusion about average value of $v^2$

I know that expected value of velocity means $$\langle v\rangle=\frac{d\langle x\rangle}{dt}$$ and since I know how to calculate $\langle x\rangle$ namely $$\langle x\rangle=\int_{-\infty}^{\infty}x|\...
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0answers
30 views

Velocity addition formula derived from velocity boosts

I understand the derivation for the equation the velocity in a boosted frame by taking the boosts of the differentials such that: $v'^{\mu}= \frac{dx'^{\mu}}{dt'} $ where $x^{\mu} = \Lambda^{\mu}_{\, \...
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1answer
49 views

Dynamically changing acceleration of object moving towards sun due to gravity

For a collection of sci-fi short stories set in the rather near future I need an approximation of the time it would take a space ship to travel from an Earth orbit to Ceres. In a previous story of ...
0
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1answer
11 views

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 ...
4
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3answers
915 views

Why isn't acceleration always zero whenever velocity is zero, such as the moment a ball bounces off a wall? [duplicate]

The answer to this homework problem is $\left(\text{D}\right) :$ I understand why we rule out options $\left(\text{A}\right)$ and $\left(\text{B}\right)$ first. However, I don't get why $\left(\...
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2answers
103 views

The chain rule and velocity transformation in relativity

From elementary calculus, we have that the chain rule occurs when we differentiate a function like $f(y(x)) \equiv f(x)$: $$\frac{\mathrm{d}}{\mathrm{dx}}[f] = \frac{\mathrm{d}}{\mathrm{dx}}[f(y(x))] ...
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1answer
38 views

Spring mass system

While solving some spring block questions one doubt came in my mind ..is it possible to calculate maximum velocity of a point between two springs of different force constant attached to a block of ...
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1answer
47 views

How fast will air travel to fill a vacuum?

Suppose I have a sealed glass cylindrical vessel of radius r and length l that is evacuated. I smash one end. How long will it take for air to (a) reach the end of the cylinder (b) fill the vacuum ...
2
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3answers
104 views

What happens to $P = F × v$ for a car moving on a frictionless surface and in vacuum?

I'm considering a scenario in which a car with an engine capable of producing maximum power of 200 hp is moving on a frictionless surface and in vacuum. Since no work is lost due to friction or air ...
1
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1answer
28 views

Signs in relative vector addition

So I know the formula for relative vector addition is $$w = \frac{v-u}{1-\frac{uv}{c^2}}.$$ How do I chose when to use this formula or its inverse transformation for solving vector addition problems ...
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2answers
55 views

How does the mass distribution and center of gravity affect the speed of a lego car down a ramp? [closed]

we are doing a research involving motion of an object with a nonuniform mass distribution, and we have to explain how mass concentration, mass distribution, and center of gravity will affect a Lego ...
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1answer
44 views

In the equation for acceleration (with known $v$, $u$ and $s$) why velocity is squared and displacement is multiplied by 2? [closed]

In the following equation $$a = \frac{v^2 − u^2 } {2s} ,$$ where $v$ is the final velocity, $u$ is the initial velocity, and $s$ is displacement. Why is velocity squared and displacement multiplied by ...
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2answers
22 views

Confusion on Horizontal & Vertical Components of a Parabolic Motion

This was a question I found about projectile motion, the question was what's the bike's speed when it took off. Using $S=ut + 0.5at^2$, the time taken to reach the ground is $0.505 s$, they used ...
0
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1answer
88 views

A basic question on Heisenberg uncertainty and experiment

I’m not a physicist or anything even close. But what I understand from the reason for the Heisenberg uncertainty is that the photon is changing the volecity/momentum when it hits the particle. ...
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2answers
48 views

What is the difference between velocity and speed? [duplicate]

What is the difference between velocity and speed? could anyone describe it more specific? does velocity have direction?
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2answers
33 views

Doubts in understanding the instantaneous velocity [duplicate]

I was studying about the fundamentals in physics and I read a defination of average velocity. It was like that average velocity is a physical quantity which gives the measure of overall rapidity of a ...
0
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2answers
81 views

The maximum velocity of an object in water [closed]

Suppose we have the mass and volume of an object, like a sphere, with density less than water. We grab it under the water and leave it, so it will fly up to the surface. What will be the maximum ...
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1answer
35 views

Which is more important for a force of the impact mass or velocity? [duplicate]

If a 2 times bigger mass collides with an object in which a 2 times smaller mass collides but with 2 times the speed which one will produce more force on the object? The object is stationary before ...
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0answers
26 views

Calculating Inital Velocity required to stablize an orbit of a moon

I am currently attempting to create a little solar system simulation and I was curious if there's a decent way to calculate what a moon or planet's initial velocity would need to be to remain in orbit ...
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2answers
31 views

How do I determine the components of a cinematic jump, for vertical and horizontal velocity?

I have been tasked with determining the feasibility of The Rock's jump in the movie 'Skyscraper' I am using projectile motion equations to determine it, but have gotten stuck whilst calculating my ...
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0answers
54 views

Pressure on the outer hull of aeroplane on theoretical emergency landing

I'm trying to figure out the proper way to calculate the pressure on the hull of aeroplane when landing on water. Let's say the horizontal velocity of plane is $1000$ km/h and it starts free-falling ...
1
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1answer
37 views

Is there any physical scalar potential where $U$ is also depends on $\dot q_i$s?

In the book of Classical Mechanics by Goldstein, at page 21, while deriving the Lagrange's equation, when the external forces are derivable from a scalar potential $U$, the author implicitly assumes ...
14
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5answers
3k views

I don't understand why escape velocity is necessary [duplicate]

I have read multiple explanations of escape velocity, including that on Wikipedia, and I don't understand it. If I launch a rocket from the surface of the Earth towards the sun with just enough force ...
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1answer
59 views

Rotating sphere and the velocity of particle at the surface

If a sphere is rotating with speed $\omega$ and has a radius $r$, then after one complete revolution what would be the velocity of a particle at the surface (neither at topmost or point of contact of ...
2
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2answers
81 views

How and why does momentum get transferred? [closed]

Let us imagine an isolated system and there are two objects of whatever masses and size. Let one object move towards the other object with constant velocity. We know, that when they collide, the ...
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2answers
159 views

Can an object have constant speed and tangential acceleration without undergoing circular motion?

Is it possible for an object to be moving with constant speed and a constant magnitude of acceleration tangent to this velocity but NOT move in a circular path? If there are other situations could I ...
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1answer
46 views

If kinetic energy is mass times the integral of velocity, isn't it just a product of mass times distance? [closed]

I'm still learning Calculus at the moment and I'm currently on integration. The moment I realized the "$1/2$" and square value in $v^2$ are just products of integration, can't one just use ...
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1answer
70 views

What does expressing ‘velocity’ as a function of $(x,y)$ mean? [closed]

This is a question from my textbook. We have been given an equation of trajectory (equation of an ellipse), and the question wants me to express the velocity vectorially as a function of (x,y). I ...
17
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6answers
416 views

Can you jump higher if you run? If so, why? (High jumping)

I have often wondered why high jumpers can jump higher if you run. The way I see it is that you only build up horizontal speed, and since you're running on a plane, I cannot see how this speed can be ...
1
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2answers
35 views

Fastest hyperloop-like vehicle which a human could endure [closed]

I'm currently writing on a science-fiction novel where a transportation system like the hyperloop has been built. Now, I'm wondering how fast I can make this. Since the plot takes place on many ...
0
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1answer
54 views

Calculation of speed from accelerometer data

I am trying to use my accelerometer on my mobile device fitness band to find the speed of walking and running. I conducted my experiment of walking and running on treadmill where I asked a person to ...
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2answers
41 views

Instantaneous velocity applications

I refered these two questions Instantaneous velocity How to interpret instantaneous velocity using limit? and I understood how instantaneous velocity is defined. But why do we define it? Velocity ...
3
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3answers
108 views

Possible paradox relating to acceleration, velocity, and work

I recently encountered a question that made me think of this "paradox": Imagine the following situation: There are two forces: Force 1 and Force 2. They accelerate a mass $m$ from the same initial ...
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1answer
30 views

How does one calculate the energy used depending on the velocity and air resistance of an object [closed]

I'm in need of a equation that can tell me how much energy/work I need to move an object inside a low air-pressure tube. The equation should (if possible) include drag, object velocity and mass. If ...
0
votes
1answer
23 views

“Regularization” of the stationnary solution for diffusion in spherical coordinates

In spherical coordinates $(r,\theta,\phi)$, the stationnary diffusion equation is a Laplace equation $\Delta f =0$. The solution in a radial symmetry : $f=f_{\infty}-r_0/r$ where $f_{\infty}$ and $r_0$...
0
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1answer
29 views

Can I find out magnitude and direction (+starting point) of a vectror using only one method? (graphical or mathematical)

Let's say I need to find out the magnitude and direction (by the direction i mean "position of a vector"/"starting point + direction") in uniform circular motion. When I draw it into a diagram and ...
0
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2answers
117 views

Centripetal Acceleration as a Cross Product

Is it fine to express the centripetal acceleration as a cross product? a=v X w (where a is centripetal acceleration, v is magnitude of velocity, w is angular velocity) And is it v X w or w X v? ...
0
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1answer
90 views

How is four-velocity automatically normalized?

This is a page from Sean Carroll's Spacetime and Geometry.There is a line in this page which says that the four velocity is automatically normalized.This absolute normalization is a reflection of the ...
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1answer
42 views

How to Find Jerk from Discrete Velocity Data?

I have measured the velocity of an object at discrete intervals. I want to find the corresponding acceleration and jerk of the object. How do I do this with discrete values rather than continuous ...
0
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1answer
44 views

How fast would an object at cruising altitude (around 10,600 m) need to travel to stay on the opposite side of the Earth to the Moon? [closed]

I am trying to figure out how fast an object will have to travel (at a height around 10,600 m) to never be in the presence of the moon. Meaning the object will always be on the opposite side of the ...