# Questions tagged [velocity]

The time rate of change of the position of an object

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### Made a formula, but its pretty lengthy and need to verify it [closed]

so basically the theory on which I based this formula from was that, if object x is travelling on a plane surface for certain distance d1 , at time t1 and some velocity , then t1 is given by d1 / v1 ...
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### How to understand instantaneous velocity concept [duplicate]

When I started learning instantaneous velocity it didn't make sense to me. I don't understand in real life why we can't measure instantaneous velocity and therefore why we use this concept. Or is this ...
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### If a photon travelled in the opposite direction of another photon [duplicate]

If a photon travels in the opposite direction as another photon, then what is the speed of the second photon relative to the first. Is it 2 times the speed of light? Also what if two photons travelled ...
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1 vote
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### Why does a changing electric field propagate/travel? [closed]

So I can understand why an electric field creates a magnetic field and how these two are basically one thing - one cannot exist without the other. But why does an EM Wave travel? Scenario: We have the ...
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### Avarage velocity of a planet in a parabolic orbit

How the average velocity of a planet (over the entire time; $t = 0$ to $\infty$) orbiting a star in a parabolic orbit can be calculated? If it's instantaneous velocity is $v$ (at distance '$r$' from ...
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1 vote
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### How do I explain that there is no instantaneous velocity at a sharp turn? [duplicate]

Suppose that a one-dimensional motion is describe by the function $s(t)=\begin{cases} t , & 0 \leq t \leq 5;\\ 10 - t, & 5 < t \leq 6\end{cases}$, where $t$ is a time and $s(t)$ is the ...
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### Velocity operator, its expression and eigenvalues

Cohen Tannoudji pp 215 Third postulate :The only possible result of the measurement of a physical quantity $\mathscr A$ is one of the eigenvalues of the corresponding observable $\mathbf A$. pp 225 ...
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### What formula is used for finding the velocity of a particle, that is moving around an object with a charge density? [closed]

A particle with a mass $m$, and charge $q$, moving around an infinite wire, where the wire has some charge density, given in $nC/m$. How can I extract the relation of this information, to see how the ...
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### Acceleration is absolute — is this really true? [closed]

I've looked at the following pages: Is acceleration an absolute quantity? Is acceleration frame dependent or absolute? Is this the reason why acceleration is said absolute? I don't think any of the ...
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### Why do we write force = mass × acceleration? [duplicate]

Force is directly proportional to mass and rate of change in velocity i.e., acceleration. So why do we write force as mass times acceleration? I mean why do we multiply mass by acceleration?
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### Sine and Cosine Functions [closed]

So long story short, We were given a windmill to experiment with and a sensor could sense the Voltage produced and graph it concerning time. We decided to make a sine wave out of the positive and ...
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### Unit of $v$ in $v=rω$ [duplicate]

unit of velocity is m/sec but in $v=rω$ unit of $r$ is metre and unit of $ω$ is radian/sec so unit of $v$ should be radian*metre/sec but it is m/sec how I know this is dimensionally correct but I dont ...
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### Does only the space region movement due universe expansion affect the possibility of viewing a star?

My question is maybe simple and easy to answer because the intrinsic speed of the star affects only the final frequency of observed light but are there any tricks about the combination of object ...
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### Derivation of Ladenburg correction (to calculate viscosity of fluid with Stoke's Law)

I am creating a lab report investigating the amount of time it takes for a marble ball to sink to the bottom of a cylinder container filled with sugar syrup. I recorded the amount of time it takes for ...
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### Intuition behind $p = mv$ and $F = ma$

I am only familiar with physics at an elementary level; and while that is true, it would be nice if I could clear up some clashes with intuition I'm having before progressing further. What is the ...
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### Linear velocity is cross product of angular velocity and position

Why is linear velocity is cross product of angular velocity and position?
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### When to consider the velocity of the other reference frame?

Let's say I have a spaceship going away from the Earth with speed $V=3/5c$ and it emits a light signal back to Earth when 1h in hit it spaceship time. This is the problem presented in this video and I'...
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### Why consider velocity from our own reference frame in Einstein's Addition

I'm trying to understand Einstein's Velocities Addition concept in Special Relativity. I know how to derive the equation from Lorentz Transformations, but I'm trying to take an intuitive (or at least ...
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### Is Hubbles law due to Gravity?

Hubble's law states that Distance is proportional to Velocity. A ScienceDirect article states that Classical Hubble expansion is characterized by a proportional increase in the rate of expansion ...
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### $F=ma$. $p = mv$. What's $mx$?

So I know that $$F=ma$$ ($F$ is force, $m$ is mass, and $a$ is acceleration). I also know that $$p=m\int a dt=mv$$ (Where $p$ is momentum and $v$ is velocity). So I was wondering if the following ...
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1 vote
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### Finding radial and tangential velocity [closed]

Given $$\vec r =r\cos(θ(t))\hat i +r\sin(θ(t))\hat j$$ and $$θ(t)=t^2$$(everything in mks). I am supposed to find the radial and tangential components of the velocity at $t = 2$ seconds. But I am ...
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### Does a moving object with a constant velocity do any work?

Since Work=Force$\cdot$ Distance and the net force on a moving body is zero, does that mean that no work is done by a body moving with a constant speed? Also, the work done is the energy expended. If ...
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