Questions tagged [velocity]

The time rate of change of the position of an object

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Determining star position and velocity to deduce closest approach?

I am trying to replicate the results found for Gliese 710's closest approach of ~0.05 parsecs in 1.3 million years approximately. I thought that by plotting the sun at (0,0) and using the stars ra,dec,...
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Magnitude of Acceleration Vector when Speed is Constant

If I observe a change in direction of velocity, but not in speed: What does the acceleration vector look like? I am confused! The difference vector between two vectors of equal length A has a ...
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Why isn't the tangential velocity of circular motion zero?

Why is tangential velocity 2πr/T if the body's total displacement in the end of one revolution is zero?
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Instantaneous speed x instantaneous velocity

Related to Distinguish between instantaneous speed and instantaneous velocity I understand that the average velocity is given by the displacement divided by the change in time, and it is a vector ...
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Confusion regarding Special Relativity and Relativity of Velocity? [duplicate]

Suppose that there are two points in an empty space A and B and observers at A and B having clocks: If A were to be traveling near speed of light, when clock at A passes 1 hour, observer at A ...
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About Constrained Speeds

My question is whether there is any known method, which doesn't use calculus, to find the speed of ball C, given that the speeds of balls A and B are given at a certain moment in time. Suppose that in ...
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How do I calculate frictional forces of an object sliding laterally on a sloped plane?

Game developer here. Most problems about objects sliding down sloped planes with friction are about the object sliding in the natural downward sliding direction of the slope. But how would you ...
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Can something exceed the speed of light relative to a moving object? [duplicate]

If you fire two light beams in opposite directions, won't one of the beams be moving away from the other at twice the speed of light? Doesn't that mean you and a friend can travel at 51% of the speed ...
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Track an object velocity in a 2D plane

I would like to track the motion (actually, I am more interested in the velocity) of an object in a 2D plane (typically 4m x 4m). The object speed is typically 10cm/s, but the mouvement may be chaotic ...
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Does acceleration or deceleration affect the strength of impact if velocity is the same?

2 identical cars both hit a wall at the same exact speed (let's say 50 mph), but one car was speeding up to 50 mph and the other car was slowing down to 50 mph. Also let's assume that the cars are ...
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For the context of an investigation where velocity is unknown and you are trying to model it, can you calculate the constant $k$ without it

I was wondering in an investigation where you are trying to model velocity for eg: modelling the velocity of an entry vehicle for a space rover in mars's atmosphere. to calculate the constant $k$ ...
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Faster than light is possible? [duplicate]

I know that some particles can go near or more than half the speed of light. So, say we shoot two particles in opposite directions at more than half the speed of light. Say one is moving at 50% the ...
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If a force depends on velocity, then why is the force not conservative? I need a formal proof [duplicate]

I am currently an undergraduate taking a course on Newtonian mechanics. The lecturer defines a force to be conservative if there exists a scalar function (we call it potential function), say $V(x,y,z)$...
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Why does my 3rd method not show me that power = force dotted with velocity?

I have derived 3 expressions for the power that a force, $\vec{F}$, transfers to a body. (A) and (B) are consistent, but (C) isn't. Where have I gone wrong with (C)? EDIT: THE MISTAKE HAS NOW BEEN ...
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How to Calculate frequencies, $C$ and Group $Cg$ from a dispersion relation?

Some people requested what was the context of the question and this is where it comes from: "Given the dispersion relation: $w^2=w_0^2+A^2k^2$ ( $w_0$ and $A$ are constants) Which frequencies ...
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If falling coconut has more momentum than a bullet then why bullet is more deadly? [closed]

Imagine a coconut of mass 1kg is falling from a 10m tall tree, the momentum is around 14kg.m/s (I don't know how to format my work but just trust me) and then the momentum of a bullet of mass 0.01kg ...
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Paradoxical result arising regarding velocity

I was working on a problem that goes like this Bob beats Judy by 10 m in a 100-m dash. Bob, claiming to give Judy an equal chance, agrees to race her again but to start from 10 m behind the starting ...
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Why is it that objects inside a moving train tend to move at the same speed as the train itself?

I mean I get people saying because it's Newtonian mechanics. Everything inside the train will have same speed as that of train but my question is why ? Why is it like that ? And How does that happen ? ...
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What's the fastest speed water from a glacial dam burst could achieve? [duplicate]

I've been watching a lot of Graham Hancock videos of late, thrusting myself deep into the rabbit hole of pseudoarchaeology/alternative archaeology, and I don't really know enough to assess the ...
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What does instantaneous velocity mean? [duplicate]

What does instantaneous velocity mean? on google it says "Instantaneous means something happens very quickly, in a single moment. It's similar to the meaning of "instant", but most ...
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Critical velocity of a fluid

Critical velocity($v$) of a fluid is given by $v = \frac{Rr}{\rho\eta}$ where, $R \rightarrow$ Reynolds number $r \rightarrow$ Radius of tube $\rho \rightarrow$ Density of fluid $\eta \rightarrow$ ...
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How can position of charge moving under magnetic field have different positions for different observers

Assume we have a point charge $Q$ moving with velocity $\vec{v}$ with respect to an observer at rest and is in the presence of magnetic field $\vec{B}$. $\vec{B}$ and $\vec{v}$ are perpendicular to ...
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Given a distance, and velocity as a function of time, how do I find the time taken to travel the distance? [closed]

Given the velocity of a particle as a function of time V(t), and a distance between two points on a straight line (from point A to point B), I would like to find the time it will take the particle to ...
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How is velocity defined for different systems?

I'm currently a beginner learning classical mechanics, and I just learned about the Lagrangian formalism. I completely understand the theory behind it, but a lot of times, I'm not able to calculate ...
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Understanding velocity as a vector quantity [closed]

Why is velocity classified as a vector quantity. Can it be explained by the same way as force referring to the Phys.SE post Where am I confused about force addition?
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1 answer
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How to find rest mass?

I have two identical massess with rest mass $m_0$. One of them is made to move with very high velocity $v$, while other is at rest. At some point in time the moving mass collides with the stationary ...
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What is the error in the following way of finding phase difference between two sound waves? [closed]

Consider the 2 incoherent sound waves, $$S_1 = S_0\sin{(\omega_1 t-k_1 x)}$$ $$S_2 = S_0\sin{(\omega_2 t-k_2 x)}$$ Phase difference: $$\Delta\phi = \omega_1 t-k_1 x -\omega_2 t+k_2 x$$ Using $kv=\...
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Stationary Obversers in Brinkmann Coordinates

The four-velocity of a stationary observer is defined as $U^{u}$ = $\left (\dot{t},0,0,0 \right )$, where t is the time coordinate in some four-dimensional coordinate system, and overdot represents ...
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Formula for adding velocities in opposed motion at relativistic speeds from the perspective of a stationary observer

I'm confused by the formula 𝑢=(𝑣+𝑣′)/(1+𝑣𝑣′/𝑐^2) whenever I apply it to a specific thought experiment. I have a third party, stationary observer, who observers to collinear objects moving ...
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Drone in an elevator

I just watched this video, What Happens If You Fly a Drone In An Elevator? Real Experiment! To my surprise, the answer was not what I expected. I thought the drone would stay stationary. My thought ...
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Coriolis force relation to wind velocity

I'm learning coriolis effect on Winds moving from equator towards North pole. This is for geography. Question: Why is coriolis force stronger for winds having larger speed(larger component of ...
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In a uniformly accelerated motion experiment, the acceleration can be attained from $V_{ave}$ vs. $t/2$ and $x$ vs. $t^2$ graph. How is this possible?

Specifically, in the experiment, we had to release a glider from an inclined plane (that had an angle of inclination of 10 degrees). We had to calculate the time it reaches the final position. We had ...
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Is there a mistake in this special relativity question? Partial derivative

I’m not asking for the answer or even how to solve it — I just want to know if there has been a mistake. Given $$U^\alpha = (1+t^2, t^2, \sqrt{2}\,t,0)$$ Show that (using the “brute force” method) $$...
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Why doesn't the frequency of a cyclotron make an impact on the radius of the path of a charged particle?

The cyclotron frequency is given by $$f=\frac{qB}{2πm}$$ Obviously this equation has nothing to do with the radius. But my question is, when the frequency increases, shouldn't the velocity increase, ...
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Equivalence of inertial frames of reference and lorentz transform derivation [duplicate]

I trying to understand Lorentz transformation derivation, and confuse on a simple statement: If i have 2 frame of reference, and the second moves relative to the first with speed $V$, so relative to ...
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Lorentz transform causes Faster than light motion for Spacelike-separated object?

Consider a 5-meter rod which exists on the x-axis of a frame of reference: Now consider an observer moving at a velocity $0.1c$ relative to this reference frame, from right to left. Their frame of ...
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Interpretation of velocity-velocity and acceleration-acceleration curves

I am parametrizing equations of motion in the form: $$x(t) = x_0+v_{0,x}t\\y(t) = y_0+v_{0,y}t+\frac{1}{2}at^2$$ The parametrized equation with respect to time: $$y(x) = y_0+v_{0,y}\cdot \frac{x - x_0}...
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10 answers
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Why does force perpendicular to the velocity change only its direction; not the speed?

While analyzing the case of a force and consequently an acceleration acting perpendicular to the velocity of a given body, I do understand that force's component along the velocity will be 0 causing ...
Nilaay's user avatar
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7 answers
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Definition of four-velocity: why define it with proper time of the object?

The four-velocity(world-velocty) is defined by : $u^μ=\frac{dx^μ}{dτ}$ ,where $τ$ is the proper time of the object. I don't understand why it's defined with respect to the proper time but not the time ...
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1 answer
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Calculating linear velocity based on the (Euler) rotation matrix having 2 time indices

Normally, we denote a rotation matrix with respect to time as $R(t)$. As I understand, we can only denote like that because the initial observation is assumed to be zero ($t_0 = 0$) and $t$ is ...
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Product of two 4 positions without writing the components

I was able to solve the first part of the following question by expanding the terms as vectors I can't understand how to do it without expanding so I had a look at the answers. I understand how we ...
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Relative velocity motion in this case

Take a look at this picture, the point $a$ is the location of the wheel's center in the robot's frame {$0$}. The point $c$ is attached to a robot's mass center. The angular velocity $\omega$ is the ...
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Why don't boundary layers have a transverse pressure gradient due to the Bernoulli effect?

This is something I always thought about but never truly understood. A boundary layer has a velocity gradient, $\partial u/ \partial y$. The Bernoulli principle states that pressure and velocity are ...
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Question about the norm of the four-velocity being equal to $c$

On the way to the Einstein equation we derived the four-velocity: $$u^\mu=(c,v^k)$$ with $v^k$ being the 3-velocity, which can can be very low ($ |v|<<c$). However, the square of the four ...
Fuzzy's user avatar
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Can generalised momentum be defined as mass times generalised velocity? [closed]

The generalised momentum is defined by the partial derivative of Lagrangian. Can we think of this as a mass times a generalised velocity?
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Wording of Relative Velocity problems [closed]

I've been doing some relative velocity problems. The three main types I do are to do with cars, boats/rivers and planes/crosswind. I'm fine with cars as the wording is pretty straightforward - it is ...
Jay Chen's user avatar
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2 answers
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Centripetal acceleration with constant speed

If a particle is moving in a circular path at a constant speed, how can we represent its centripetal acceleration? Since the speed is constant, I assume that the centripetal acceleration describes how ...
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1 answer
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Position-time graph of two cars is given [closed]

So this was a test question, I answered that both cars have the same acceleration. Since the graphs for A and B both are straight lines, therefore, the acceleration of both must be zero. But the ...
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Where to find the article(s) saying that 3D Navier-Stokes solutions exist in case of a small initial velocity?

I've already been searching for here and on the internet, maybe not enough. PS: this result is stated in the Clay Mathematics Institute N-S problem definition, page 2: https://www.claymath.org/wp-...
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2 answers
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Collision Calculation in 2D

For a 2D physics simulation, I need to resolve collisions between two objects in 2D. I have available each object's initial angular velocity, linear velocity, mass, moment of inertia, and center of ...
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