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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Why isn't velocity operator given as $\mathbf v=\mathbf {\frac{d\hat R}{dt}}$ [duplicate]

Cohen-Tannoudji pp 223 The observable $\mathbf A$ which describes a classically defined physical quantity $\mathscr A$ is obtained by replacing, in the suitably symmetrized expression for $\mathscr ...
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What does graph look like if velocity is discrete quantity?

This sound silly question. If velocity is continuous quantity when we plot graph of falling object ( distance VS time ) it would be smooth curve and velocity VS time would be straight line but I ...
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While derivating equations of motion, why do we replace $v$ as $u + at$?

I was learning about the calculus derivations of equations of motion. After the derivation of $v=u + at$, where $v =$ final velocity and $u =$ initial velocity, came the 2nd Equation of motion. In my ...
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Instantanous and uniform velocity and acceleration

If the mathemical expression of instantanous velocity is $d/t$, what is the mathematical expression of uniform velocity. If the mathematical expression of instantanous acceleration is $v/t$, what is ...
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Rail gun muzzle velocity

Don't know to ask it in this community or not but, is there any formula to calculate the muzzle(escape) velocity of rail gun? and another question We know that plasma is conductive so we can use ...
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Velocity required to hit coordinate $(x, y)$ at 45° [closed]

I create a top-down game where the character is able to throw things. For the input I use a joystick that gives me a direction to shoot and a magnitude. The magnitude between 0 and 1 (that I map ...
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3 answers
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The case of an initial velocity greater than final velocity with a drag force proportional to the velocity squared

consider an object with a mass $m$ falling in a fluid with a drag force proportional to its velocity squared $(f=kv^2)$. the governing differential equation can be found using Newton's second law of ...
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Does car move when instantaneous velocity is zero? [duplicate]

In 3blue1brown: derivative paradox. supposed car moving with: $S(t) = t^3$ And velocity is: $V(t) = 3t^2$ He asked when t = 0 velocity is 0 m/s , does that car move at that time ? And here his ...
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What happens to the velocity of a radioactively decaying object?

Suppose that I have a lump of a radioactive material, like Uranium-235. I put it in an ideal box, which perfectly isolates the inside from the outside - no radiation escapes the box and the outer ...
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If a plank is moving horizontally on a solid cylinder with a spring attached to it on a wall, why is its velocity twice the velocity of the cylinder? [closed]

Pretty much the title, why is the velocity of the plank on the cylinder twice the velocity of the cylinder?
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Calculate pipe size and friction loss for an agricultural project? [closed]

I'm in the process of designing a water system for our regenerative agricultural project in the Horn of Africa. I'm looking to install a ≈1000L water tank on a 3 meter stand which will gravity supply ...
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Calculating average speed as weighted mean

In the books it says that average speed is just s/t. But I am wondering if we can calculate average speed using weighted average mean, using time or using length of path? For instance, if we know that ...
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Is a velocity-dependent force $\vec{F}$ that doesn't do any work on an object a conservative force? [duplicate]

Let's consider a point like object with mass $m$ upon which acts a force $\vec{F} = \vec{c} \times \vec{v}$ ($\vec{c}$ is supposed to be a constant vector). Given that $\vec{F}$ is perpendicular to $\...
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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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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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How to convert acceleration to velocity when the acceleration itself is changing?

I am trying to simulate a rocket and I don't really understand how to convert acceleration to velocity when it is changing constantly. This is my acceleration chart where $x_1$ is time in seconds and $...
3 votes
1 answer
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Error in Manipulating $4$-Velocities?

Suppose a particle travels with velocity $\textbf u=(c/3,c/4)$ as perceived in an inertial frame $S$. Let $S'$ be another inertial frame at speed $c/5$ in the direction of the positive $x$-direction (...
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1 answer
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Understanding relativistic velocity addition

For objects with a speed much lower than the speed of light, you can simply add and subtract velocities based on their vector orientation to one another. I'm aware that this does not apply to ...
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1 answer
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Derive Newton's Law of Gravitation from Kepler's 3rd Law, Assuming an Elliptical Orbit? [closed]

Can you derive Newton's law of gravitation from Kepler's third law, assuming an elliptical orbit? Most of what I've seen have been people solving it with a circular orbit. However, I find it ...
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Linear and angular velocity of a falling rod in the corner of a room [closed]

A uniform rod of length l and mass m is sitting vertically in a frictionless environment in the corner of a room, having a floor beneath it, and a wall to its left. It gets slightly off balance and so ...
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Does everything move through spacetime at the same speed? [duplicate]

It seems to me that this article ("What’s the real reason you can’t go faster than the speed of light?", Big Think, November 17, 2022) is wrong or misleading in claiming that every object ...
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If $I = naevd$ where $v$ is the drift velocity then why in photoelectric effect increase potential across plates only increase current for a while?

Just studying photoelectric effect and got this confusion.
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1 answer
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Pound-Rebka Experiment

I am new here and have a question. Does anyone know if the velocity of the photons changes in the Pound-Rebka experiment? Do the wavelength and the frequency change simultaneously, so that there is no ...
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Kinematics and electrostatics [closed]

Suppose we have two opposite charges of charge $+4 \cdot 10^{-5}\,$C and $-4 \cdot 10^{-5}\,$C and mass 5$\,$g each, at a distance of 1$\,$m. Now if they were released from rest then, all the ...
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Clarification over Instantaneous Velocity and the Shape of a Curve

Assume a ball sliding down a curve with no friction. Conventional thinking would suggest that the steeper the curve, the faster the ball will roll down. But when I derive the formula for velocity, I ...
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How do you calculate velocity reduction over time due to drag, when drag is also a function of velocity?

The drag equation is: $F_D=\frac12 \rho C_d A v^2$, assuming constant values let's simplify to $F_D=Cv^2$ Assuming there are no other forces to consider, I'm really not sure where to go from here. I ...
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Windspeed and Aeroplanes

Say we had an airplane cruising at velocity $V$ and the airplane was going from point $A$ to $B$. If the wind was also blowing in the same direction from $A$ to $B$, at a velocity $U$, could we say ...
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Can inverse velocities add? [closed]

Everyone here probably saw once the question of a container being filled with multiple hoses each at it's own speed, or maybe lumberjacks working or machines or whatever, the question usually goes ...
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Work required to change an object's speed in different reference frames

Let $\vec s$, $\vec v$, $\vec a$ and $\vec F$ be displacement, velocity, acceleration, and force functions of time $t$. With respect to a absolute reference frame, such that $\vec v = \vec 0$ at $t = ...
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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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Why is it called drift velocity and not drift speed?

Why is the average rate at which electrons cover the length of a conductor called drift velocity? Wouldn't it being called drift speed be more fitting as that would remove all notions of the conductor'...
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