Questions tagged [velocity]

The time rate of change of the position of an object

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What is displacement time graph for this object which is in $xy$ plane going in sine wave like path from A to B. Also can velocity constant in path?

The path is from A to B in sine wave curve while the displacement is straight line.So how displacement is calculated for graph purpose here
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Can an object move with a constant velocity without balanced forces?

Can an object move with a constant (magnitude) velocity without the balanced forces? As an object which is balanced with the frictional force continues moving at a constant velocity, acquired till ...
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Probability of observing harmonic oscillator at a particular position

Consider a classical harmonic oscillator whose Hamiltonian is $$H=\frac{p^2}{2m} +\frac{1}{2}mw^2x^2$$ where $w$ is the oscillating frequency. I wish to find the probability of observing the harmonic ...
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What is the instant velocity? [duplicate]

The velocity is the variation rate of the position correct? So does it make sense to talk about velocity without time?
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Changing velocity even when acceleration is zero

Consider a particle performing circular motion with position given by $$\vec r=r_0e^{\beta t}\hat r$$ such that $\dot\theta=\omega$, is a constant. The velocity becomes $$\vec v=\beta r_0e^{\beta t}\...
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Konig's Theorems

In the proof of Konig's Theorems the following identity is used: $$ \underline{v_i} = \underline{v_i'} + \underline{v_c} $$ which is the law of transformation of velocity when passing from the ...
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Can the speed of the wind influence the speed of sound propagated in it?

The question came up with a exercise (Page 5, exercise (vi) of Pratice Exercise 1.1) from the book Physics Galaxy Volume 1 Ed. 1, Ashish Arora. The question proposes the following: Two junglemen are ...
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If two object moving away from each other, does one object see the other slower than their relative speed?

Let's say I am on spaceship A and it is moving with speed of 0.6c. Also, there's other spaceship B which is moving with the speed of 0.4c opposite direction from me. And after some time in our travel, ...
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Does the speed of an object underwater change when viewed above?

Let's say a submarine is coming to surface with a velocity $v$ normal to the surface of water and let's say you are the admiral of the navy viewing the submarine from the top. The submarine is exactly ...
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How to find time taken for a faster object to cross a slower object of same length, both moving parallel to each other in the same direction? [closed]

Can you explain me how to determine the time taken for a faster object to cross a slower object when they're both of same length and are moving parallel to each other in the same direction?
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What happens to the motion of the body if acceleration equal zero? [closed]

$If$ the body moves with $variable$ velocity and $variable$ acceleration ,but at a certain instant the $acceleration$ was zero then we can say at this instant the body moves with constant $velocity$ $?...
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Length contraction and acceleration in opposite directions

If you accelerate in a direction, objects in front and behind you get closer relative to you. If you then accelerate again in the opposite direction, the same thing happens, which leads to a ...
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Does the kinetic energy theorem imply that any body on wich is exerted the same space-dependent force is equally accelerated?

So, we have a body $P_1$ of mass $m$ that travels from $A$ to $B$ along a straight line, on wich is exerted a constant force $F$ dependent only on the position of $P_1$. We know that the work done is $...
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Does this special relativistic identity hold in General Relativity?

So I came across the following identity in the fascinating book: "Beyond the Einstein Addition Law and it's Gyroscopic Thomas Precession": $$\gamma_{u \oplus v} = \gamma_u \gamma_v\left(1 + \...
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Maximum height reached by an object

Here, in the last line, from the formula s is negative, but how can s be negative? Also, should it not be s=u^2/2g instead of s= - u^2/2g?
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Angular velocity of a ball if force is applied above its center

I am wondering what the angular velocity would be if you apply a force over time to a ball above its center (but not tangential). For instance, if a ball of was lying on a flat surface and you apply a ...
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Why is acceleration not usually count as a state? [duplicate]

Position, velocity and acceleration can vary over time. Although only position and velocity are usually count as states of the ODEs. Which makes me wonder why acceleration is not taken as a state?
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On what ground do you multiply $m$ with $v$ in the momentum equation $p=mv$? [duplicate]

I've read several other posts that says the momentum equation is the definition of momentum, and it has no proof. However, I would like to know what is the experimental observation where the ...
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Free-body-diagram of a falling ball

The free-body-diagram of a falling ball where air resistance is not negligible, is the drag force ever greater than the weight of the ball? I mean mustn't it as it is slowing down? But then how is the ...
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Velocities - Equation 1.46 of Goldstein 3rd edition

In his derivation of the Euler-Lagrange equations from D'Alembert's principle, Goldstein uses the parametrization (equation 1.45') $$\displaystyle{\vec{r_i}=\vec{r_i}(q_1,q_2, ..., q_n, t)}\tag{1.45'}$...
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Why does velocity change or accelerate in the presence of force?

I know that $F=ma$, but why? Why does velocity change in the presence of force? Please answer it based on the fundamental level if possible.
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What is the terminal velocity of coin

Very little work has been done at my office for the past few weeks, as we've been bogged down in a debate on the terminal velocity of a coin (the coin in question is a local one, of 9.2g, 28.5mm ...
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The resultant force on a simple pendulum bob

At the equilibrium position of an oscillating pendulum, its acceleration is momentarily zero as the velocity reaches its maximum value. Does this mean that at the equilibrium position the resultant ...
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How does the clock postulate apply in non-inertial frames?

I've read countless answers and other sources on the question of whether time dilation is caused both by velocity and acceleration or only by velocity, but they all look at things only from an ...
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When the mass flux is constant, why does $ v d\rho = - \rho dv$?

I'm reading about mass fluxes and I came across when the mass flux is constant $$ j = \rho v$$ then the following equation is true $$ v d\rho = - \rho dv$$ What does that last equation even represent? ...
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How to fill the gap in this derivation of proper acceleration without four vectors?

I've scoured this site, the web, and some books for derivations of the formula for proper acceleration as a function of coordinate acceleration ($\alpha = \gamma^3 a$) without four vectors or ...
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How to calculate velocity vector from scalar angular velocity and position vector in 2D?

I would like to know, if I have an angular velocity as scalar, how can I calculate the velocity vector. I know that the product of angular velocity and the length of the distance gives the speed, but ...
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Deducing the velocity field of wind from the motion of plants

I am developing a project for the subject of fluid mechanics and I had a question. The project we want to develop involves using wind and a small hill as a giant wind tunnel. The hill is filled with ...
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Does it actually make sense to talk about velocity of the point of contact of a wheel rolling without slipping?

I was reading this answer where I saw the following gif: We can see that when a point becomes point of contact (i.e: touching the ground), the curve of it's motion has a cusp. To my knowledge, a cusp ...
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2 answers
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Where does this derivation of the velocity addition theorem go wrong?

Situation: We consider two inertial systems $1$ and $2$ in standard configuration, i.e. system $2$ is moving into the direction $x_1$ with a speed of $v$. We only consider one spatial axis. An object ...
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How to interpret a displacement-position graph?

I have a good understanding of Displacement-time graphs and position-time graphs and how to interpret them. I take the IB diploma and came across this question from a 2009 paper with a displacement-...
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Is kinetic energy formula tightly related to Pythagoras theorem?

Consider 2 balls of mass $M$ traveling on the plain at speed $V$. One ball goes up and the other goes right. Let's associate them with the vectors $(V, 0)$ and $(0, V)$ to express their velocity and ...
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Velocity of a boat after getting off of it

A 50 kg person gets off of a 100 kg boat at rest with a velocity of 10 m/s. What will be the velocity of the boat in the opposite direction? Apparently, the momentum of the person and the boat are ...
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Why is addition of velocities under a Lorentz-transformation associative and commutative for when boost are in same direction?

I'm working with Lorentz transformations, and one of the problems I encountered needed a derivation of the velocity of a particle $u$ in a stationary reference frame S, in the variables $u'$, which is ...
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What is the difference between velocity of wave and velocity of pulse on a string wave?

I have read in my textbook that velocity of a wave remains constant but then there was a question to find velocity of pulse as a function of x in a vertically hanged rope.(where x is the position of ...
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Is it possible for a point-like system to behave like $x(t) = \frac{t}{2}\log(t^2)$ near $t=0$? (infinite speed) [closed]

Is it possible for a point-like system to behave like $x(t) = \frac{t}{2}\log(t^2)$ near $t=0$? (infinite speed) I know beforehand that relativity theory forbids anything with mass from travel faster ...
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Method of averaging velocities of electron when deriving drift velocity

Here is derivation of drift velocity. Assume there is a field $\vec{E}$ inside the conductor(wire). Using equations of motion we can say that for every charge inside the conductor, $$\vec{v_1}=\vec{...
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3 answers
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How do you find the final velocity when acceleration is changing between two values over some distance? [duplicate]

How do you calculate a final velocity of an object when given its initial velocity and the object is accelerating between an initial and final acceleration over some given distance?
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Velocity gradient in a liquid

When we consider the motion of fluid in terms of many thin layers sliding over each other , we say that layer at a top of a layer forces it to move forward while layer below a layer forces it to move ...
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How to Calculate speed of body required for collision to have specific output

I'm trying to calculate the speed the bolt of an airsoft rifle has to go in order for a bb to have a specific speed. for example: the bb weighs 0.2g and the bolt I have weights 100g, I would like the ...
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Terminal velocity of a metal sphere in water

I am trying to figure out the terminal velocity of a metal ball dropped into water or oil. After searching a bit on the internet, I came to the conclusion that I needed to use Stokes' Law and ...
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3 answers
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Why is the speed of near speed of light moving particles not over the speed of light?

I've been looking for an answer to this question for a while now and I've seen the mathematical explanation $$Vr=[V1+V2]/[1+V1*V2/c²]$$ I understand that the result cannot be greater than $c$ because ...
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How is there kinetic energy at the bottom of the pendulum swing if velocity = 0 at the lowest point?

Say a mass $m$ is attached to a massless string that is attached to the ceiling. The mass is pulled 30 degrees to the left of the vertical and then let go. At the lowest point of its swing it has ...
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Object starts moving and stops moving?

An object starts moving at point $a$ at $t_a$, and stops at point $b$ at $t_b$ with constant velocity $\vec v$. Does this sentence mean the objects accelerate tremendously from $0$ at $t_a$ to $\vec v$...
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Finding how much a larger body slows down when it collides with a number of much smaller bodies

A larger spherical body collides with a number of much smaller spherical bodies. I've just seen this equation, and was wondering if anybody could explain it to me: $$\Delta v =1-\frac{1}{1+\pi R^2n\...
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3 votes
7 answers
156 views

What exactly is rest?

Consider a position-time graph for a particle's motion, where the y-axis is position and the x-axis is time (in seconds). Now, consider the question: At what point in time is the particle at rest? ...
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1 answer
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Angular velocity after collision of two curling stones

I am trying to create physics for game. I think I can figure out how the stones should move after collision... however I am not sure how to figure out the angular velocity of stones after collision. ...
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2 answers
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Average speed / Velocity

We know that in kinematics we have the concepts about "average speed". By definition the average speed is the total of the distance divided by time, but I still don't get it what is the ...
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2 votes
2 answers
127 views

Does the speed of sound wave change when the source velocity change?

The speed of sound in air is about $740$ miles per hour. Suppose that a police car is sounding its siren and is driving towards you at $60$ miles per hour. At what speed is the sound of the siren ...
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1 answer
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Constraint rate change problem [closed]

Two small rings O and O' are put on two vertical stationary rods AB and A'B' , respectively. One end of the inextensible threads tied at point A'. The thread passes through ring O' and it's other end ...
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