# Questions tagged [velocity]

The time rate of change of the position of an object

1,216 questions
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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 ...
1answer
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### 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 ...
1answer
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### 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 ...
2answers
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### 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 ...
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: $\phi(t)$....
2answers
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 ...
0answers
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### 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 ...
2answers
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?
1answer
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### 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?
3answers
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### 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 ...
1answer
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### 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. ...
4answers
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### 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 ...
7answers
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1answer
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### 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 ...
0answers
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### 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 ...
1answer
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### 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 ...
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 ...
0answers
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### forward and angular velocity addition

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

### 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 ...
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 ...
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?
2answers
98 views

### 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 ...
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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### 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. ...