Questions tagged [velocity]
The time rate of change of the position of an object
2,262
questions
-1
votes
1
answer
51
views
Assistance interpreting equation
Given a position function of a particle:
$$
\mathbf r=r\,\hat{\mathbf r}\left(\theta\right),
$$
where $\hat{\mathbf r}(θ)$ is the polar unit vector, to find the velocity, we take the derivative which ...
-2
votes
1
answer
555
views
Can acceleration be both the "rate of increase of velocity" and the "rate of increase of speed" in Physics?
A Dictionary of Physics (Oxford University Press) defines acceleration as:
The rate of increase of speed or velocity
However, from reading many other definitions it seems to me that acceleration ...
0
votes
2
answers
430
views
What to call an object which is in motion but not accelerating?
I began learning about acceleration and according to the source i learned from an object only accelerates when there is change in vel. &/ direction... what i am wondering is what do you call it ...
3
votes
2
answers
2k
views
Can a body be in equilibrium when only one force acts on the body? [duplicate]
I think that when we throw a body in air, at top point the body is in equilibrium but gravitational force is still acting. Is this correct?
2
votes
2
answers
1k
views
How come group and phase velocity can be different in a non-dispersive media?
I'm a (ex-)physicist working in the applied-physics world and was digging into group vs phase velocities.
There is one thing that confuses me : when would that be the case where group and phase ...
2
votes
2
answers
2k
views
Terminal velocity to calculate velocity as a function of time?
Using the equation for drag force,
$F = c_d \times \rho \times v^2 \times A \times \frac{1}{2}$,
where $c_d$ is coefficient of drag, $\rho$ is air density, $v$ is terminal velocity, and $A$ is ...
0
votes
0
answers
71
views
Maxwell-Boltzman speed distribution
For a class assignment, I have to do a Barnes-Hut Galaxy simulation.
The assignment includes:
The dots' velocities following the Maxwell distribution with typical velocity of $$v={\left<v\right&...
0
votes
2
answers
1k
views
Relativistic equation for motion in a constant acceleration
I found many questions regarding relativistic velocity addition and the relative formula
$$V_{x} = \cfrac {V_{x}^{'} + v}{1+\cfrac{vV_{x}^{'}}{c^{2}}}$$
but I found none concerning velocity ...
1
vote
1
answer
95
views
Distance traveled by accelerating vehicle
Let's say I'm trying to model a train accelerating from speed $v_1$ to speed $v_2$, where the train's mass $m$ and engine power $P$ is known. I would like to find both the time $t$ and the distance $s$...
3
votes
1
answer
83
views
Special Relativity Question: Massive particle racing light
I'm a bit rusty on my special relativity and have been thinking about this problem recently:
Suppose that a massive projectile (i.e. something large enough that we could see with a telescope) is ...
0
votes
1
answer
97
views
Velocity and mass and particles
If mass increases as velocity increases how can I associate this with the fact that some particles such as neutrinos which barely have no mass, go faster when they have less mass or less interaction ...
-1
votes
4
answers
1k
views
Direction of velocity in curvilinear motion [closed]
My textbook mentions that the direction of net instantaneous velocity is along the tangent to the curve. Well, from the polar coordinate system I also know that the net instantaneous velocity has two ...
3
votes
2
answers
441
views
Velocity vector for helical motion? [closed]
Problem describes a point particle moving in an upwards helix, with the velocity in the $z$-direction being a constant 3 m/s and circular uniform motion in $xy$-plane along a circle with radius = 6 m ...
1
vote
4
answers
2k
views
Why does the wavelength of a particle go down with higher velocity?
In mechanical waves, the wavelength increases with a higher velocity.
λ = v / f.
And the wavelength in particles lower with a higher velocity.
λ = h / mv.
2
votes
1
answer
191
views
How to calculate the position of a fluid parcel knowing the Eulerian velocity
I know the velocity of a fluid, $V(\mathbf x,t)$ for each fixed point $\mathbf x$ and time $t$. From this information, I want to calculate the position in time, $L(t)$, of a fluid parcel that was at ...
0
votes
2
answers
4k
views
Calculating Velocity from Acceleration (Accelerometer)
I am using the Accelerometer in an Android Device to track and detect certain motions, using only one axis as the motions are linear along that axis.
I am using a simple filter to remove the noise ...
5
votes
1
answer
520
views
How to find 4-velocity components in a perturbed metric?
Beginning with a metric with small perturbations
\begin{eqnarray}
g_{00} &=& 1-2\frac{U}{c^2} + \mathcal{O}(c^{-4}) \\
g_{0i} &=& \mathcal{O}(c^{-3}) \\
g_{ij} &=& -\delta_{ij}\...
0
votes
1
answer
618
views
When and how do we use the formula Power = force X velocity?
I'm unable to understand the solution given in this book mine... Why are we adding the resistive force? In fact, i would really appreciate if someone explains the question to me, I'm really struggling ...
-2
votes
2
answers
260
views
Are mass and velocity complementary
Are mass and velocity complementary? I would like to know if there is a Heisenberg uncertainty relationship between the two.
[EDIT]
No answers so I thought I would expand a little.
The reason I ...
1
vote
0
answers
628
views
Using the Kalman filter given acceleration to estimate position and velocity [closed]
I am reading data from an accelerometer. I want to use this data to estimate velocity and position. Originally, I performed a double integration of acceleration to read this data, and as confirmed by ...
1
vote
2
answers
346
views
Deriving the boundary condition for this flow
The Question:
Suppose a circular cylinder of radius $a$ moves with constant velocity $U$ in the $x$-direction in a two-dimensional irrotational, incompressible flow whose velocity decays to zero at ...
2
votes
1
answer
731
views
What (conceptually) is "Four Velocity"?
Too many text books (in fact, all of them that I've found including 'Gravity'), just throw out the term Four Velocity without digging into what it means, exactly. I understand $\frac{dx}{dt}$, but I ...
-3
votes
2
answers
284
views
Kinematics problem invloving position and time [closed]
An object is moving along X axis with position as a function of time given by $x = x(t)$. Point $O$ is at $x = 0$. The object is definitely moving towards $O$ when
1. $\mathrm dx/\mathrm dt < 0$
...
0
votes
2
answers
4k
views
Calculation of polar velocity components given cartesian counterparts
I would like to calculate the polar velocity components given the position $(x,y)$ and velocity $(u_x,u_y)$ in Cartesian coordinates. First of all,
$$
r=\sqrt{x^2+y^2}\text{ and }\theta=\tan^{-1}\left(...
-1
votes
2
answers
328
views
How instantaneous speed is defined as magnitude of instant velocity? [closed]
Let $s=$distance (a variable)
we define instantaneous speed = magnitude $\left[\frac{ds}{dt}\right]$.
However instantaneous speed is also defined as magnitude of instantaneous velocity
i.e. ...
2
votes
2
answers
509
views
Applying Lorentz Transformation
Lorentz Velocity Transformation:
$$v_x = \frac{v_x' + u}{1+\frac{uv_x'}{c^2}}\tag1$$
$$v_x' = \frac{v_x - u}{1-\frac{uv_x}{c^2}}\tag2$$
The speed of spaceship and scoutship are given relative to ...
0
votes
1
answer
65
views
Velocity question which involved forward difference and back difference
Suppose one person at $t_0$ is at the location $p_0$
at $t_1$ is at the location $p_1$
at $t_2$ is at the location $p_2$
Then question:
this person velocity at $t_1$ is $(p_1-p_0)/(t_1-t_0)$
Or $(...
1
vote
1
answer
75
views
Speed of Light and Relative Velocity [duplicate]
Yesterday I was going through the idea of Relative Velocity in which, when the bodies are moving in opposite directions, their velocities add up. So, if one of the bodies in consideration is light, ...
2
votes
2
answers
972
views
Question about the physical meaning of normalization of 4-velocity
I'm struggling with a concept of normalization of 4-velocity in Special Relativity (and General Relativity eventually).
Well, after a bunch of introduction to vector/tensor calculus we came up with ...
0
votes
2
answers
1k
views
Uniform motion with non-uniform velocity
Let's suppose that there is a body which is moving with non-uniform velocity in the straight line. In the first hour it travels with a velocity of 50 km per hour and in the second hour it stops for 30 ...
0
votes
2
answers
112
views
How to calculate average velocity using a series of measurements? [duplicate]
Assuming there is a series of delta time and displacement measurements, there are two way to calculate the average velocity I can think of:
Divide total displacement by total time.
Average of all ...
0
votes
1
answer
549
views
Question about acceleration and velocity [closed]
A canoe is drifting left toward a hungry hippo with a velocity of $7 m/s$. The canoe rider starts paddling frantically, causing the canoe to travel to the right with a constant acceleration of $6 m/s^...
0
votes
2
answers
922
views
Can a falling body on earth exceed its terminal velocity in a huge vacuum container?
Im not so sure about why a body has a terminal velocity. According to my knowledge it is due to the air drag. Force created by a falling body as it accelerates downwards due to gravity when equals the ...
-1
votes
2
answers
2k
views
1D Motion: Average Velocity without Direction?
How come this solution doesn't include direction for average velocity since it is a vector?
Calculate the average velocity at a particular time interval of a particle if it is moves 5 m at 2 s and ...
1
vote
2
answers
3k
views
Looking for the Formula for Uncertainty for Velocity
In a lab I'm working on, we used a formula for uncertainty of area:
$$\sqrt{\left(\frac{δl}{l}\right)^2+\left(\frac{δw}{w}\right)^2}$$
We are asked to now find uncertainty for velocity (m/s) and the ...
0
votes
2
answers
298
views
Increasing speed of a car using more motors? [closed]
I am making a robot car with four wheels. Every wheel will be attached to a motor. If I use four motors and four wheels , will I get more speed then using two motors?(If all the motors rotate at same ...
1
vote
0
answers
90
views
How to make a car go down a ramp at contest velocity even when the angle of the ramp is changed [closed]
This is a high school project, I need to make a car go down a ramp at a contest velocity even when the angle of the ramp is changed, I was hoping if anyone could help me, figure out some way of doing ...
0
votes
1
answer
2k
views
Calculate distance an accelerometer moved
I am reading accelerometer data and want to determine the distance that the accelerometer is moved. ( My question is similar to the one placed here, Calculate speed from accelerometer . I just feel as ...
-2
votes
1
answer
2k
views
Pendulum hanging from moving wagon [closed]
My Question is: What is the equation describing the angle of the pendulum (theta) depending on the time depending position of the wagon(x(t)).
theta( t, x(t) ) = ?
Note: Neglecting any sort of ...
0
votes
1
answer
2k
views
What is the magnitude of acceleration given $v_i$, $v_f$, and $x$?
I'm really struggling with this question that is part of my physics assignment. Any help would be appreciated.
This is the question:
A speed skater moving to the left across frictionless ice at 8.4 ...
1
vote
0
answers
516
views
Gravity and rotating torus
Questions:
Would a spinning torus lose its weight?
Would a solid torus, spinning at 7,81 km/s radial speed completely loose it's weight on Earth-like object?
Would it 'fly away' at higher speeds?
{...
1
vote
1
answer
230
views
Speed, velocity, and momentum of light
As far as I understand speed is a rate of travel and velocity is a directional rate of travel.
The equation for momentum is given as follows $$p=mv$$
Where $m$ is mass and $v$ is velocity.
Case 1. ...
-1
votes
1
answer
31
views
projectiles-kinematics
Let's just say that I have two identical spheres at the same height. Both of them are given the same push (same velocity). One of the spheres is projected vertically upward and the other is projected ...
17
votes
7
answers
6k
views
What's the difference between average velocity and instantaneous velocity?
Suppose the distance $x$ varies with time as:
$$x = 490t^2.$$
We have to calculate the velocity at $t = 10\ \mathrm s$.
My question is that why can't we just put $t = 10$ in the equation $$x = 490t^2$...
0
votes
2
answers
2k
views
Propulsive Power, Thrust and Velocity
If my rocket requires thrust $T$ to maintain a velocity $v$, the propulsive power can be calculated using
$$P=Tv$$
Assuming the same friction (so the required thrust to maintain the velocity doesn't ...
0
votes
1
answer
80
views
Relation of velocity and angular momentum in quantum mechanics
in quantum mechanics (non-relativistic or relativistic), when the angular momentum of the particle change is the velocity effected?
are we assume the angular momentum equal zero when we determinate ...
1
vote
1
answer
1k
views
Calculating velocity of electrons in a vacuum tube (read description)
If I use a high voltage DC current in a vacuum tube to bring a lower power AC current into a vacuum tube, how do I calculate the average velocity of the AC electrons?
13
votes
4
answers
3k
views
What would qualify as a deceleration rather than an acceleration if speed is unchanged?
The instantaneous acceleration $\textbf{a}(t)$ of a particle is defined as the rate of change of its instantaneous velocity $\textbf{v}(t)$: $$\textbf{a}(t)=\frac{\mathrm{d}}{\mathrm{d}t}\textbf{v}(t)....
0
votes
1
answer
261
views
Direction of Friction of a cup on a table cloth [duplicate]
I'm having a bit of trouble figuring out which direction kinetic friction is supposed to act in.
A glass of water is placed on a cloth at distance d from the table edge, and the cloth is spread out ...
1
vote
1
answer
307
views
Difference between gravity and wind in simulation [closed]
So this is more of a conceptual question for simulations.
I have gravity in my simulation that is going to the side: $g=(0,10)$.
I know that gravity is acceleration.
But is wind acceleration (...