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Questions tagged [velocity]

The time rate of change of the position of an object

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Correlation between velocity and homogeneity of spacetime and isotropy of space

Considering only inertial frames of reference and constant velocities, does the fact that any velocity, with the exception for the speed of light in a vacuum, can be transformed, via an accurate ...
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1answer
69 views

Conservation of angular momentum during rolling with slipping [closed]

A block of mass m moves with a velocity $\mathbf{B}$ on a smooth horizontal surface. It then passes over a cylinder $R$ and mass $m$, capable of rotating about it's own axis through $O$. The block ...
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44 views

How a particle move with a constant velocity from rest? [closed]

How can a particle move with a constant velocity from rest? I know that the net force on a particle that moves with a constant velocity is zero, so how will it move from rest with a constant velocity ...
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72 views

Moving a charge with constant velocity

How can we make a positive test charge move with a constant velocity from infinity if the source charge is positive? I know that when a particle moves with a constant velocity velocity the net force ...
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0answers
117 views

Analytical mechanics, constant angle between velocity and acceleration [closed]

A particle moves in a plane so that the angle between velocity and acceleration is constant $\alpha$. Angle $\phi$ between velocity and fixed coordinate axis varies according to a given law: $\phi(t)$....
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125 views

The relation between speed and wavelength

I was taught categorically that the velocity of a wave depends only on the medium in which it travels. Now I just stumbled upon a sentence + formula that declares that "the velocity of sinus-waves ...
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25 views

Minimum Time Through Curve

Consider the following conditions: A level road with the path $\vec{r} = \left<x(s),\ y(s)\right>$ A max speed of $v_{max}$ A vehicle with the mass $m$ Tires with a static friction coefficient ...
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475 views

If an object moves at constant speed, does it necessarily have constant velocity? [closed]

If an object moves at constant speed, does it necessarily have constant velocity?
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49 views

If two bodies move constantly but with different speed, do they move with acceleration relative to each other? [closed]

If two bodies move constantly but with different speed, do they move with acceleration relative to each other?
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34 views

How is velocity defined in circular motion in central force field?

In my view the velocity is change of displacement in the increasing direction of displacement. Now in circular motion in central force field the particle is changing its direction then how is the ...
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1answer
24 views

Expressing average velocity in terms of acceleration

Average velocity is usually expressed as the displacement divided by the time. For example, $$v_{\text{avg}} = \frac{x(t)-x_0}{t}$$ I have not, however seen it expressed in terms of acceleration. ...
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4answers
98 views

Is there an agreed upon physics definition of the term 'speed'?--for example, can it be negative?

The term speed is commonly defined as follows: https://www.physicsclassroom.com/class/1DKin/Lesson-1/Scalars-and-Vectors Speed, being a scalar quantity, is the rate at which an object covers ...
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Why isn't average speed defined as the magnitude of average velocity?

Speed is usually defined as the magnitude of (instantaneous) velocity. So one could assume that average speed would be defined as the magnitude of average velocity. But instead it is defined as $$s_{...
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Kinetic Energy with constant velocity

I am sorry for the question, but I am a noob in Physics. I don't understand why in the kinetic energy's formula the distance is out of the equation. Kinetic Energy formula: $$K = \frac{1}{2}m v^2 = ...
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1answer
67 views

Intuition behind group velocity

Why is the group velocity of the wave given as $\frac {\partial w }{\partial k}$? I understand what the group velocity means but its always given as a definition and I would like to have some ...
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19 views

Calculating velocity of a negative charge

From my First Year Physics Textbook: Q1 and Q2 are stationary charges of 7.5x10^-6 Coulomb each. Point P is a mobile charge of -1.6x10^-6 Coulomb, with mass 2x10^-6 kg. Based on a previous part of ...
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1answer
51 views

Which is more efficient in stopping a bullet, small cubes or fine grains of sand

Recently, I was presented with the following problem, relating to pressure: which would be more efficient in stopping a bullet, small cubes or fine grains of sand. Using my intuition, I would say the ...
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2answers
34 views

What is the speed of rotation of the magnetic field of a solenoid or current-carrying WIRE

How does one find the speed of rotation of the magnetic field around a current-carrying wire? or How fast is it circulating around the wire? How does one identify the speed of rotation of the ...
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20 views

forward and angular velocity addition

I share some data here which is related to my question. ...
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1answer
67 views

How to calculate the radius of a curve based on vehicle wheel speeds of a car

I have data of the 4 differen wheelspeeds of a vehicle during driving time. Based on that I want to calculate the radius of a curve it is taking. The following are my current thoughts that seem to be ...
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2answers
52 views

Speed of two objects orbiting around a central axis

This question has been bugging me for quite some time and i'm not too sure if i'm missing out some important factor in the understanding of this scenario: Given two objects of equal mass and size ...
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1answer
44 views

For a fluid travelling in a tube, if the pressure is decreased at a constant temperature, how does it affect the velocity and fluid density?

I am interested in understanding the relationship between pressure and velocity, as well as pressure and fluid density. I know that the principle of Bernoulli states that there exists a relationship ...
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1answer
50 views

Which relation is correct for resultant instantaneous velocity in 2d?

Please forgive me if the following question sounds silly and I can't exactly pin point where exactly the problem is but there is some problem with my understanding of vectors. In Cartesian ...
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1answer
49 views

Assistance interpreting equation

Given a position function of a particle: $$ \mathbf r=r\,\hat{\mathbf r}\left(\theta\right), $$ where $\hat{\mathbf r}(θ)$ is the polar unit vector, to find the velocity, we take the derivative which ...
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1answer
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Can acceleration be both the “rate of increase of velocity” and the “rate of increase of speed” in Physics?

A Dictionary of Physics (Oxford University Press) defines acceleration as: The rate of increase of speed or velocity However, from reading many other definitions it seems to me that acceleration ...
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2answers
124 views

What to call an object which is in motion but not accelerating?

I began learning about acceleration and according to the source i learned from an object only accelerates when there is change in vel. &/ direction... what i am wondering is what do you call it ...
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2answers
907 views

Can a body be in equilibrium when only one force acts on the body? [duplicate]

I think that when we throw a body in air, at top point the body is in equilibrium but gravitational force is still acting. Is this correct?
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How come group and phase velocity can be different in a non-dispersive media?

I'm a (ex-)physicist working in the applied-physics world and was digging into group vs phase velocities. There is one thing that confuses me : when would that be the case where group and phase ...
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2answers
82 views

Terminal velocity to calculate velocity as a function of time?

Using the equation for drag force, $F = c_d \times \rho \times v^2 \times A \times \frac{1}{2}$, where $c_d$ is coefficient of drag, $\rho$ is air density, $v$ is terminal velocity, and $A$ is ...
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28 views

Maxwell-Boltzman speed distribution

For a class assignment, I have to do a Barnes-Hut Galaxy simulation. The assignment includes: The dots' velocities following the Maxwell distribution with typical velocity of $$v={\left<v\right&...
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2answers
172 views

Relativistic equation for motion in a constant acceleration

I found many questions regarding relativistic velocity addition and the relative formula $$V_{x} = \cfrac {V_{x}^{'} + v}{1+\cfrac{vV_{x}^{'}}{c^{2}}}$$ but I found none concerning velocity ...
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1answer
38 views

Distance traveled by accelerating vehicle

Let's say I'm trying to model a train accelerating from speed $v_1$ to speed $v_2$, where the train's mass $m$ and engine power $P$ is known. I would like to find both the time $t$ and the distance $s$...
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1answer
71 views

Special Relativity Question: Massive particle racing light

I'm a bit rusty on my special relativity and have been thinking about this problem recently: Suppose that a massive projectile (i.e. something large enough that we could see with a telescope) is ...
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Fluid velocity due to differential pressure (pipe in pipe) to equilibrium

I would like to calculate the velocity of fluid drop (and change over time (iterative)) to calculate the time taken for an unbalanced hydrostatic column to reach equilibrium. Something that I have ...
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65 views

Deriving group velocity from restoring force and density

I have seen that in some cases one can derive the group velocity of a wave quickly by identifying the restoring force in the system and the density of the medium that the wave is traveling through (e....
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1answer
40 views

Velocity and mass and particles

If mass increases as velocity increases how can I associate this with the fact that some particles such as neutrinos which barely have no mass, go faster when they have less mass or less interaction ...
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4answers
155 views

Direction of velocity in curvilinear motion [closed]

My textbook mentions that the direction of net instantaneous velocity is along the tangent to the curve. Well, from the polar coordinate system I also know that the net instantaneous velocity has two ...
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2answers
63 views

Velocity vector for helical motion? [closed]

Problem describes a point particle moving in an upwards helix, with the velocity in the $z$-direction being a constant 3 m/s and circular uniform motion in $xy$-plane along a circle with radius = 6 m ...
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4answers
108 views

Why does the wavelength of a particle go down with higher velocity?

In mechanical waves, the wavelength increases with a higher velocity. λ = v / f. And the wavelength in particles lower with a higher velocity. λ = h / mv.
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1answer
50 views

How to calculate the position of a fluid parcel knowing the Eulerian velocity

I know the velocity of a fluid, $V(\mathbf x,t)$ for each fixed point $\mathbf x$ and time $t$. From this information, I want to calculate the position in time, $L(t)$, of a fluid parcel that was at ...
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2answers
436 views

Calculating Velocity from Acceleration (Accelerometer)

I am using the Accelerometer in an Android Device to track and detect certain motions, using only one axis as the motions are linear along that axis. I am using a simple filter to remove the noise ...
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1answer
120 views

How to find 4-velocity components in a perturbed metric?

Beginning with a metric with small perturbations \begin{eqnarray} g_{00} &=& 1-2\frac{U}{c^2} + \mathcal{O}(c^{-4}) \\ g_{0i} &=& \mathcal{O}(c^{-3}) \\ g_{ij} &=& -\delta_{ij}\...
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1answer
50 views

When and how do we use the formula Power = force X velocity?

I'm unable to understand the solution given in this book mine... Why are we adding the resistive force? In fact, i would really appreciate if someone explains the question to me, I'm really struggling ...
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2answers
90 views

Are mass and velocity complementary

Are mass and velocity complementary? I would like to know if there is a Heisenberg uncertainty relationship between the two. [EDIT] No answers so I thought I would expand a little. The reason I ...
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0answers
120 views

Using the Kalman filter given acceleration to estimate position and velocity [closed]

I am reading data from an accelerometer. I want to use this data to estimate velocity and position. Originally, I performed a double integration of acceleration to read this data, and as confirmed by ...
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2answers
63 views

Deriving the boundary condition for this flow

The Question: Suppose a circular cylinder of radius $a$ moves with constant velocity $U$ in the $x$-direction in a two-dimensional irrotational, incompressible flow whose velocity decays to zero at ...
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1answer
114 views

What (conceptually) is “Four Velocity”?

Too many text books (in fact, all of them that I've found including 'Gravity'), just throw out the term Four Velocity without digging into what it means, exactly. I understand $\frac{dx}{dt}$, but I ...
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2answers
105 views

Kinematics problem invloving position and time [closed]

An object is moving along X axis with position as a function of time given by $x = x(t)$. Point $O$ is at $x = 0$. The object is definitely moving towards $O$ when 1. $\mathrm dx/\mathrm dt < 0$ ...
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1answer
55 views

Calculation of polar velocity components given cartesian counterparts

I would like to calculate the polar velocity components given the position $(x,y)$ and velocity $(u_x,u_y)$ in Cartesian coordinates. First of all, $$ r=\sqrt{x^2+y^2}\text{ and }\theta=\tan^{-1}\left(...
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2answers
85 views

How instantaneous speed is defined as magnitude of instant velocity? [closed]

Let $s=$distance (a variable) we define instantaneous speed = magnitude $\left[\frac{ds}{dt}\right]$. However instantaneous speed is also defined as magnitude of instantaneous velocity i.e. ...