Questions tagged [velocity]
The time rate of change of the position of an object
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If I run along the aisle of a bus traveling at (almost) the speed of light, can I travel faster than the speed of light?
Let's say I fire a bus through space at (almost) the speed of light in vacuum. If I'm inside the bus (sitting on the back seat) and I run up the aisle of the bus toward the front, does that mean I'm ...
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31
votes
6
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(Almost) double light speed
Let's say we have $2$ particles facing each other and each traveling (almost) at speed of light.
Let's say I'm sitting on #$1$ particle so in my point of view #$2$ particle's speed is (almost) $c+c=...
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Velocity in a turning reference frame
I often see the relation that $\vec v=\vec v_0+ \vec \omega \times \vec r$ in a turning reference frame, but where does it actually come from and how do I arrive at the acceleration being $$\vec a=\...
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Why does the (relativistic) mass of an object increase when its speed approaches that of light?
I'm reading Nano: The Essentials by T. Pradeep and I came upon this statement in the section explaining the basics of scanning electron microscopy.
However, the equation breaks down when the ...
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Why does a free-falling body experience no force despite accelerating?
Note: For the purposes of my question, when I refer to free fall assume it takes place in a vacuum.
From my (admittedly weak) understanding of the equivalence principle, falling in a gravitational ...
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How to derive addition of velocities without the Lorentz transformation?
Lorentz contraction and time dilatation can be deduced without Lorentz transformation. Can you deduce also the theorem of addition of velocities
$$w~=~\dfrac{u+v}{1+uv/c^2}$$
without Lorentz ...
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Understanding terms Twist and Wrench
In kinematics, physics and especially robotics, we often encounter the terms Twist and Wrench. Twist is (LinearVelocity, AngularVelocity) and Wrench is (Force, Torque). The reason I'm confused is I ...
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Does a moving object curve space-time as its velocity increases?
We always hear how gravity bends space-time; why shouldn't velocity?
Consider a spaceship traveling through space at a reasonable fraction of the speed of light. If this spaceship, according to ...
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4
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Explanation that air drag is proportional to speed or square speed?
A falling object with no initial velocity with mass $m$ is influenced by a gravitational force $g$ and the drag (air resistance) which is proportional to the object's speed. By Newton´s laws this can ...
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Elastic collision between two circles [duplicate]
I am trying to calculate the final velocities of two equal mass 2-dimensional circles after an elastic collision. I have tried to figure it out using formulas I know from high school physics, but ...
user99752
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Why does cancellation of dots $\frac{\partial \dot{\mathbf{r}}_i}{\partial \dot{q}_j} = \frac{\partial \mathbf{r}_i}{\partial q_j}$ work?
Why is the following equation true?
$$\frac{\partial \mathbf{v}_i}{\partial \dot{q}_j} = \frac{\partial \mathbf{r}_i}{\partial q_j}$$
where $\mathbf{v}_i$ is velocity, $\mathbf{r}_i$ is the ...
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3
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How can an object's instantaneous speed be zero and it's instantaneous acceleration be nonzero?
I'm studying for my upcoming physics course and ran across this concept - I'd love an explanation.
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Is there an intuitive explanation for why Lorentz force is perpendicular to a particle's velocity and the magnetic field?
The Lorentz force on a charged particle is perpendicular to the particle's velocity and the magnetic field it's moving through. This is obvious from the equation:
$$ \mathbf{F} = q\mathbf{v} \times \...
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Functional derivative in Lagrangian field theory
The following functional derivative holds:
\begin{align}
\frac{\delta q(t)}{\delta q(t')} ~=~ \delta(t-t')
\end{align}
and
\begin{align}
\frac{\delta \dot{q}(t)}{\delta q(t')} ~=~ \delta'(t-t')
\end{...
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Are velocity and acceleration smooth quantities?
My thinking:
acceleration corresponds to a force which is instantaneous, so the acceleration of a rigid body can be rather spiky (non-smooth)
velocity (angular velocity) describes the ratio of ...
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