Questions tagged [velocity]

The time rate of change of the position of an object

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Tangential Velocity of a Wheel Connected to a Rigid Link While Passing the Ramp [closed]

As seen in the figure, the rigid link moves at constant velocity (V) on the x-axis. This rigid link is connected to the tractor on the x-axis from one end and to the wheel from the other end with ...
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Coriolis force relation to wind velocity

I'm learning coriolis effect on Winds moving from equator towards North pole. This is for geography. Question: Why is coriolis force stronger for winds having larger speed(larger component of ...
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In a uniformly accelerated motion experiment, the acceleration can be attained from $V_{ave}$ vs. $t/2$ and $x$ vs. $t^2$ graph. How is this possible?

Specifically, in the experiment, we had to release a glider from an inclined plane (that had an angle of inclination of 10 degrees). We had to calculate the time it reaches the final position. We had ...
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Is there a mistake in this special relativity question? Partial derivative

I’m not asking for the answer or even how to solve it — I just want to know if there has been a mistake. Given $$U^\alpha = (1+t^2, t^2, \sqrt{2}\,t,0)$$ Show that (using the “brute force” method) $$...
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Why doesn't the frequency of a cyclotron make an impact on the radius of the path of a charged particle?

The cyclotron frequency is given by $$f=\frac{qB}{2πm}$$ Obviously this equation has nothing to do with the radius. But my question is, when the frequency increases, shouldn't the velocity increase, ...
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Equivalence of inertial frames of reference and lorentz transform derivation [duplicate]

I trying to understand Lorentz transformation derivation, and confuse on a simple statement: If i have 2 frame of reference, and the second moves relative to the first with speed $V$, so relative to ...
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Lorentz transform causes Faster than light motion for Spacelike-separated object?

Consider a 5-meter rod which exists on the x-axis of a frame of reference: Now consider an observer moving at a velocity $0.1c$ relative to this reference frame, from right to left. Their frame of ...
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Interpretation of velocity-velocity and acceleration-acceleration curves

I am parametrizing equations of motion in the form: $$x(t) = x_0+v_{0,x}t\\y(t) = y_0+v_{0,y}t+\frac{1}{2}at^2$$ The parametrized equation with respect to time: $$y(x) = y_0+v_{0,y}\cdot \frac{x - x_0}...
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Why does force perpendicular to the velocity change only its direction; not the speed?

While analyzing the case of a force and consequently an acceleration acting perpendicular to the velocity of a given body, I do understand that force's component along the velocity will be 0 causing ...
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Definition of four-velocity: why define it with proper time of the object?

The four-velocity(world-velocty) is defined by : $u^μ=\frac{dx^μ}{dτ}$ ,where $τ$ is the proper time of the object. I don't understand why it's defined with respect to the proper time but not the time ...
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Calculating linear velocity based on the (Euler) rotation matrix having 2 time indices

Normally, we denote a rotation matrix with respect to time as $R(t)$. As I understand, we can only denote like that because the initial observation is assumed to be zero ($t_0 = 0$) and $t$ is ...
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Product of two 4 positions without writing the components

I was able to solve the first part of the following question by expanding the terms as vectors I can't understand how to do it without expanding so I had a look at the answers. I understand how we ...
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Relative velocity motion in this case

Take a look at this picture, the point $a$ is the location of the wheel's center in the robot's frame {$0$}. The point $c$ is attached to a robot's mass center. The angular velocity $\omega$ is the ...
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Why don't boundary layers have a transverse pressure gradient due to the Bernoulli effect?

This is something I always thought about but never truly understood. A boundary layer has a velocity gradient, $\partial u/ \partial y$. The Bernoulli principle states that pressure and velocity are ...
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Question about the norm of the four-velocity being equal to $c$

On the way to the Einstein equation we derived the four-velocity: $$u^\mu=(c,v^k)$$ with $v^k$ being the 3-velocity, which can can be very low ($ |v|<<c$). However, the square of the four ...
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Can generalised momentum be defined as mass times generalised velocity? [closed]

The generalised momentum is defined by the partial derivative of Lagrangian. Can we think of this as a mass times a generalised velocity?
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Wording of Relative Velocity problems [closed]

I've been doing some relative velocity problems. The three main types I do are to do with cars, boats/rivers and planes/crosswind. I'm fine with cars as the wording is pretty straightforward - it is ...
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Centripetal acceleration with constant speed

If a particle is moving in a circular path at a constant speed, how can we represent its centripetal acceleration? Since the speed is constant, I assume that the centripetal acceleration describes how ...
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Position-time graph of two cars is given [closed]

So this was a test question, I answered that both cars have the same acceleration. Since the graphs for A and B both are straight lines, therefore, the acceleration of both must be zero. But the ...
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Where to find the article(s) saying that 3D Navier-Stokes solutions exist in case of a small initial velocity?

I've already been searching for here and on the internet, maybe not enough. PS: this result is stated in the Clay Mathematics Institute N-S problem definition, page 2: https://www.claymath.org/wp-...
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Collision Calculation in 2D

For a 2D physics simulation, I need to resolve collisions between two objects in 2D. I have available each object's initial angular velocity, linear velocity, mass, moment of inertia, and center of ...
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What is Wald talking about here in his book "General Relativity"?

I'm reading General Relativity by Robert Wald and his notation is confusing me. On page $61$ of the book, Wald claims that by setting $c=1$ we can derive $E=mc^2$ from the following information. (1) $...
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Is $u^{\mu} = \gamma\tfrac{dx^{\mu}}{dt}$ a 4-vector?

I understand that $c\dfrac{dx^{\mu}}{ds}$ is a 4-vector since $ds$ is a scalar. In flat space-time, $$ ds = c\dfrac{dt}{\gamma} $$ so $\gamma\dfrac{dx^{\mu}}{dt}$ would be a 4-vector as it is equal to ...
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What to do when the time interval is negative? Should its magnitude only be considered or should it be rejected?

Two bodies are dropped from the same point at different times. I am asked when they meet. The answer I get is -4 seconds. How do I interpret this? I think that a time interval $t_2-t_1$ always has to ...
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Why is it "forbidden" to use EM waves as a way of detecting motion in two different inertial frames?

Constant motion can not be detected by neither particles (because of inertia) nor mechanical waves ( because they need a medium ). However when you consider light for example and assume it does not ...
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Maths behind red/blue-shifting [closed]

I watched this video of silly science facts, on of which stated "you can avoid red lights by travelling at around 114,000,000mph (51,000,000m/s) because the red light would be blue shited enough ...
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Procedure to accurately extract the instantaneous velocity and spin information from experimental position data?

I have the time information of 3D position data (discrete) of a sports ball in flight, and I'm attempting to extract the velocity and spin information just using that data as I believe every ...
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Relativistic Velocity-addition formula adds a scalar to a vector?

Sorry if this is a stupid question. The formula for relativistic Velocity-addition is $u = (v + u') / (1 + (vu'/c^2))$ It seems that v, v', u, and u' are vectors, while c is a scalar. But 1 seems to ...
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Why Is Wind Energy Velocity Cubed Instead of Squared?

Formula for everything seems to be squared, for example, kinetic energy $KE = \frac{1}{2}mv^2$ But for wind energy, this formula is cubed, e.g. $\frac{1}{2}\rho A v^3$ I couldn't find any results for ...
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Lorentz Transformation of Wave Equation

Consider a 1D Wave equation: $$\frac{\partial^2 y}{\partial t^2}=v_1^2\frac{\partial^2 y}{\partial x^2}$$ So, we are given two frames, S and S' (moving along $x$-axis) with velocity $V$ relative to S. ...
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In general relativity, how to get geometric velocity from 4-vector velocity field?

Currently, I‘m listening to the lecture of Prof. Hughes (https://ocw.mit.edu/courses/8-962-general-relativity-spring-2020/video_galleries/video-lectures/). In General, I‘m able to follow the lecture, ...
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Meaning of relative rapidity

What is the meaning of relativity rapidity? I know that the rapidity of a particle in general is defined as $\text{tanh}^{-1} \left( \frac{v}{c} \right) = \phi$. I encountered a problem that talks ...
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In circular motion is acceleration vector and $\frac{dv}{dt}$ the same?

I was studying a book in which they have written this $$ a = -w^{2} r \hat{e} + \frac{dv }{dt} \ddot{e} \tag{1} \label{1}$$ Where $a$ is acceleration vector $\hat{e}$ is unit radial vector and $\ddot{...
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Velocity-Dependent Forces and Generalized Potential

Is there any theorem about for which velocity-dependent forces a velocity-dependent generalized potential of the form $$F_k=\frac d {dt} \left(\frac {\partial U}{\partial \dot q_k}\right)-\frac {\...
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Questions regarding the derivation procedure of the Karman-Howarth-Monin relation

I was reading the book "Turbulence" written by Uriel Frisch (1995) and got stuck in following the proof of the Karman-Howarth-Monin relation. Although there is already a thread about it, I ...
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How to find acceleration given power, velocity and mass?

Suppose we have an ideal vehicle with mass $m$ and power output $P$. Under ideal conditions, without friction, when the engine is running, $P$ is the time derivative of the kinetic energy of the ...
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Is it correct to say that a particle in the box can only acquire discrete velocities?

My thermodynamics lecture script says the following: Translational Energy Levels In addition to electronic energy, atoms have translational energy. To find allowed translational energies we solve Ψ ...
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Variation of height above the ground and speed

A ball is dropped from rest and falls towards the ground. Air resistance is negligible. What is the graph that shows the variation with speed of the height of the ball above the ground? Here's my ...
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Why the free Lagrangian does not dependent on the velocity vector direction, only its speed?

For freely moving particle, It's said $L$ can't depend on the velocity vector, but only its magnitude. Question: I'm looking for the contra-argument. Let's say $L$ depends on velocity vector. Then, ...
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Why do we have momentum?

Momentum is the defined as the product of mass and velocity and can be thought as measuring how much motion something has. However, it is not clear to me why we need momentum and why force is not ...
Quin Gardiner Bax's user avatar
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1 answer
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Calculating upwards drift velocity of hydrogen in air, where is the error in my calculations?

I have the following problem: I'm charging a lead-acid battery in a container. The charger could fail, producing too many amperes at too many volts. Too many amperes I can easily handle in a fuse, so ...
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Three velocity and three acceleration of particle

The following is written in $c=1$-units. Imagine that a particle is moving on a world line, parametrically described with its proper time as follows: $$t(\tau) = b^{-1}\sinh(b\tau) \text{ ; } x(\...
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Shouldn't acceleration of a car be due to kinetic friction? [closed]

During pure rolling when the car is at a constant velocity the velocity of the bottom part of the tire will be 0. But if we push on the gas we apply an angular acceleration on the tire. So now the ...
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Doubt in displacement time graph for a body moving with constant, negative velocity

This is a displacement - time graph of a body having constant, negative velocity. As we can see, the angle $θ$ (in anti - clockwise direction) is greater than $270^\circ$, and lesser than $360^\circ$,...
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Average angular velocity and speed

Are the magnitude of average angular velocity and the value of the average angular speed always same? If not then can you please give an example.
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When a person falling reachs terminal velocity, the body moves in a constant velocity. But shouldn't the body not move bcs there are equal forces?

Why is the person not staying stationary in the air when there is equal forces from both sides?
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1 answer
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How Long For An Object To Catch Up To Another Object Moving At Different Speeds? [closed]

Example: A bear is 10 m away from a person, the bear is moving at a speed of 15 m/s, the person is moving at a speed of 6 m/s, how long would it take for the bear to catch up to the person? I'm not ...
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How can the equation for generalized force be derived assuming the system is in equilibrium?

I have been going over sections 1.4-1.5 of Goldstein's Classical Mechanics where the equation for generalized force \begin{equation} Q_j=-\frac{\partial U}{\partial q_j} +\frac{d}{dt}\frac{\partial U}{...
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Geometric definition absolute velocity in affine spaces

currently I am reading the following paper by Halvorson and Clifton (https://arxiv.org/abs/quant-ph/0103041) where they try to argue that localizable particles are inconsistent with relativistic ...
dancingqueen's user avatar
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In relation to Newtonian physics, can an object's movement still be affected by extreme temperature when in a vacuum?

I'll try to keep it short: Can an object (such as a ship or shuttle) be slowed by extreme temperature when in the vacuum of space, or is temperature irrelevant at that point due to the nature of a ...
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