What is Velocity: Definition and 1000 Discussions

The velocity of an object is the rate of change of its position with respect to a frame of reference, and is a function of time. Velocity is equivalent to a specification of an object's speed and direction of motion (e.g. 60 km/h to the north). Velocity is a fundamental concept in kinematics, the branch of classical mechanics that describes the motion of bodies.
Velocity is a physical vector quantity; both magnitude and direction are needed to define it. The scalar absolute value (magnitude) of velocity is called speed, being a coherent derived unit whose quantity is measured in the SI (metric system) as metres per second (m/s or m⋅s−1). For example, "5 metres per second" is a scalar, whereas "5 metres per second east" is a vector. If there is a change in speed, direction or both, then the object has a changing velocity and is said to be undergoing an acceleration.

View More On Wikipedia.org
Recent contents Top users
  1. chucho11028

    Find the rate of change of velocity

    Hello everyone, I have a problem where I have to find the final displacement and final velocity which I have found however, I want to post few variations for that same problem which I am curious. It is more for my own knowledge > I would appreciate any help Please follow graph below with...
  2. Adec

    Comp Sci Galaxy simulation with the velocity Verlet algorithm

    To simulate the trayectories of solar systems around a black hole (i.e. a galaxy) I have 3 classes in C++: cSystem, cBlackHole and cGalaxy. cSystem assigns initial values of position, velocity, etc to a solar system. cBlackHole does the same but just for the black hole. And cGalaxy mixes...
  3. nomadreid

    I Lorentz boost -- speed or velocity?

    The Wikipedia article on Lorentz transformations is a bit confusing by its using speed and velocity almost interchangeably: of course γ (Gamma) stays the same, but (letting c=1) t'=γ(t-vx) , then if this is v⋅x, and x stays the same, then there would be a difference if something were going away...
  4. twilder

    I Scalar product of biharmonic friction with velocity components

    I know that taking the scalar product of the harmonic (Laplacian) friction term with ##\underline u## is $$\underline u \cdot [\nabla \cdot(A\nabla \underline u)] = \nabla \cdot (\underline u A \nabla \underline u) - A (\nabla \underline u )^2 $$ where ##\underline u = (u,v)## and ##A## is a...
  5. E

    I Velocity Vector Transformation from Cartesian to Spherical Coordinates

    Hi all, I can't find a single thing online that translates a cartesian velocity vector directly to spherical vector coordinate system. If I am given a cartesian point in space with a cartesian vector velocity and I want to convert it straight to spherical coordinates without the extra steps of...
  6. S

    Calculating Mean Velocity: Is Re Above 4000 Really Turbulent?

    First calculate mean velocity: 400 hl h-1 = 40,000 L / h-1 = 666.67 L/min 1L/min = 10^ -3 m3/min 666.67 L/min = 0.666 m3/min = 0.0111 m3/sec Cross sec area = (3.14)(0.1/2)^2 = 7.853 x 10^-3 m2 0.0111/7.853 x 10^-3 = 1.413 m/s Re = (1010)(1.413)(0.05)/0.0025 = 28,542.6 Am i right here? Re...
  7. ZD_zainy

    Angular velocity of a rolling object

  8. Arman777

    I The magnitude of a four velocity

    I want to clarfiy some ideas, so let us assume an inital observer measures a 4 velocity of an object. ##\vec{u} = (c\gamma_u, \gamma_uu^x, \gamma_uu^y, \gamma_uu^z)##. When we calculate the magnitude of the 4-velocity we get, $$\vec{u} \cdot \vec{u} = -c^2\gamma_u^2 + \gamma_u^2U^2$$ where...
  9. M

    MHB Method of least square: initial position & velocity

    Hey! :o A point is moving linearly with constant velocity $v$ and the movement is $x=a+vt$. The below information is given: Find the initial position $a$ and the velocity using the method of least square. Could you give me a hint how we use this method here? Couldn't we use the data of...
  10. G

    To find the true velocity of wind from relative velocity

    Please can I ask for help with the following as to where I'm going wrong. Book answer is 20 knots and 315 degrees My solution: In the below diagram I have sketched the two situations, k is the true speed of the wind. First question is, is my diagram correct? The velocity of the wind...
  11. W

    B Measurement of an unknown velocity vector of a closed space

    Hi I found this paper on the measurement of unknown velocity vector of a closed space. Does it mean that it is possible to measure the unknown velocity vector of a closed space ? Can someone explain it to me
  12. V

    Finding the y-component of a velocity vector

    The first thing I did, was to find the equations for player A (p) and ball's (b) path (for each i and j component I used the equation I wrote in the relevant equations) and then I found the derivative of both equations so I could have the velocity: $$\vec{r}_p(t)=(6t^2+3t)\hat{i}+20\hat{j}...
  13. P

    Solving for earthquake transit time via Snell's Law

    I was told to solve the second equation above for x to get l2 and l2, but that only gets me those in terms of other unknowns. I'm assuming I just need to solve t for my knowns, but I keep getting caught up by my unknowns. i.e., solving for x gives x = (l2*L*v2)/(l1*v1+l2*v2). Please note "l" is...
  14. Ennio

    I Solar wind velocity and corrections

    Greetings, how do - the velocity distribution of the solar wind at 1 AU - the velocity distribution of the solar wind in our line of sight look like? I have found the 400 Km/sec but no further information. Is it an average values? Is this radially on the sun the same? Links with graphs are...
  15. J

    What is the kinetic energy when an object reaches escape velocity?

    What is the kinetic energy equal to during the escape velocity? Henceforth, what is exactly happening at the escape velocity in terms of gravity?
  16. patric44

    Derivation of the velocity of bloch electrons

    Hi guys I saw that equation of the velocity of electrons In a periodic potential $$ v = (1/h) grad E(k) $$ in my textbook we use in our solid state physics course without any proof or any thing and when I searched for it I found that its derived in Ashcroft book appendix E : Is there is any...
  17. K

    Average speed and average velocity

    So thing that confusses me, is what is the difference regarding the calculation of speed and velocity? In think I should use the formula I wrote above to find the average velocity, but I don't understand what the formula for average speed will be then. By the way, when using the formula above...
  18. A

    Test charge velocity in Coulomb's Law

    The force on a test charge Q due to source charge q, depends on both their velocities in addition to several other quantities. For electrostatics, the source charge is at rest (its velocity is zero) but the test charge may be moving. Then how does Coulomb's Law accommodate for this velocity of...
  19. C

    Relative velocity of the wind making a flag move

    Here it is given that the flag flutters in the direction of wind w.r.t. to man. But why would the direction of fluttering of flag would change without any tangential acceleration. Is there a pseudo force acting on it. I think the direction if fluttering should remain same.
  20. Arman777

    Finding the velocity of a relativistic rocket

    Since initally the rocket at rest I wrote $$\vec{p}^R_i = (m_0, 0,0,0)$$ and at final situation $$\vec{p}^R_f = [m_0-\varepsilon m_0 N](\gamma, v\gamma, 0 ,0)$$ $$\vec{p}^F_f = [\varepsilon m_0 N](\gamma', -u\gamma', 0 ,0)$$ After equating them I get $$1 = \gamma - \varepsilon N\gamma +...
  21. Ennio

    I Velocity correction´ formula for the rotation of the Earth

    Let´s suppose we are observing the sun and measuring some spectral lines. Does the velocity correction´s formula for the Earth include the rotational velocity components of the Sun as well? or rather are we basically measuring both velocity contributes of Earth and of Sun together (receeding...
  22. E

    How can angular velocity be independent of the choice of origin?

    In a previous thread it was concluded that both torque and angular momentum are taken about a chosen origin, and these quantities are generally not invariant under translations of the origin (since ##\vec{r}## changes but ##\vec{v}## does not, etc.). The moment of inertia tensor doesn't...
  23. rayjbryant

    Calculating the terminal velocity of a magnet falling through a copper coil

    The magnet being used % magnet dimensions [m] d = .0127; r = .00238; %mass of magnet [kg] m_w = .0017; % other constants u_0 = 1.26E-6; % permeability of free space constant T m/A g = 9.81; % gravitational constant in/s^2 %coil properties [22 gauge wire] [m] a = .00635; %radius w =...
  24. P

    Lagrangian with angular velocity not constant

    Summary:: not constant spin How could I calculate the system lagrangian in function of the generalised coordinates and the conserved quantities associated to the system symmetries? I've been struggling for the case with not constant angular velocity, but I don't realize what I have to do...
  25. DaveC426913

    B Velocity Addition: Unraveling the Mystery

    I keep getting into these discussions and finding out they are not as simple as I thought. Or at least, my math is rusty. Scenario A: Two ships are each receding from Earth at .9c in opposite directions. Since these are velocities, they should have opposite signs. That can't be right, since...
  26. IamVector

    Slope and velocity problem (difficult)

  27. IamVector

    Acceleration vs velocity graph

    for example take a look on this graph
  28. B

    Calculate the velocity when 2 progressive waves are added together

    So here is my problem I have had a go at this and get an answer of 8.34cm to be my final amplitude The next part that I have been given is to calculate the velocity of when 2 waves are added together. I'm not so sure how to go about this, this is what I have tried anyway Can someone...
  29. SpaceThoughts

    Velocity calculation of an accelerated mass based on an increasing force

    A known force is doubling (egal) over a known distance, accelerating a mass. How do I calculate the final velocity of the mass at the end of the known distance , when the mass has doubled? I don't know the time. The mass is accelerated from 0 meter and from 0 velocity.
  30. B

    Working out velocity of particle moving in SHM

    So the way I have gone about it is to assume that the equilibrium position is half way between the 2 end points, hence the amplitude of this motion is 9.3/2 = 4.65 cm Therefore the displacement of the particle when it is 2cm away from one end point should be the distance between that point and...
  31. SpaceThoughts

    Calculate the change of angular velocity

    Hi there ... How do I calculate the change of angular velocity, when demonstrating conservation of angular momentum? I mean the change of angular velocity depends on the ratio between the two (rotating) masses that moves a distance along radius, and the (rotating) mass of the system itself. In...
  32. J

    Fortran Fortran subroutine solving for the velocity and displacement of a spring

    I have a simple Fortran code for solving velocity and displacement of spring, the code works fine when writing all together without using a subroutine. but as I am learning Fortran I tried to do it using subroutine, but I keep getting errors appreciate any help in advance. program msd implicit...
  33. V

    Why does the heavier cart get greater velocity than the lighter one?

    I'm thinking some of the kinetic energy and momentum from the lighter cart transferred to the heavier.
  34. iamcgettigan

    How do you find the initial velocity of a projectile given angle/distance?

    I tried resolving the information given into vertical and horizontal components. I then tried to find time, as this is how I would find the initial velocity. However, I am unsure of how to use the angle in this problem to help solve it. I am also unsure of how to find the initial velocity only...
  35. F

    Identity involving the vectors for position, velocity and aceleration

    any tip to start?
  36. Kaguro

    Group velocity and the dispersion relation

    After noting w=vk and differentiating with respect to k, and lots of simplifying, I get: Vg = c/n +(2*pi*0.6)/(k*n) This doesn't correspond to any numerical value though...
  37. ebuwsu

    Kinematics: UAM question help finding final velocity?

    x
  38. CrosisBH

    Finding the final velocity with quadratic drag

    I chose coordinates where down is positive. So the force going up is $$F_{up} = mg - cv^2$$ $$a = g + \frac{c}{m}v^2$$ $$a = g + \frac{c}{m}v^2$$ $$a = g \left(1 + \frac{v^2}{v_t^2}\right)$$ $$a = \frac{dv}{dt} = v\frac{dv}{dy} = g \left(1 + \frac{v^2}{v_t^2}\right)$$ I used normal separation of...
  39. T

    Velocity equation for a cyclindrical tank and long pipe

    I was not really sure as to whether to ask this question here or the h/w forum as its something I am personally trying to understand. However, I shall let the admin decided. The question comes from a book called : . The specific question I have an issue with is not the question itself but the...
  40. F

    Solving Dependence of Velocity on Time: A Guide

    I could use some help with this problem. I am having trouble finding how to change the dependence from velocity to time in a).
  41. E

    Weirdness with this relative velocity formula when defining coordinate systems differently

    Wikipedia gives, "The relative velocity ##{\displaystyle {\vec {v}}_{B\mid A}}## is the velocity of an object or observer B in the rest frame of another object or observer A." Suppose the coordinate system being used in the rest frame of ##A## is has its origin slightly displaced from ##A##...
  42. T

    Vortex Nucleation Critical velocity using the Uncertainty Principle

    Hi there, I'm very stuck on this problem when approaching it like this. I know I could use the Landau Criterion for rotons but that's not accepted here, it wants the approach to come from the uncertainty principle. My thinking is along these lines: There will be a change in chemical potential...
  43. Like Tony Stark

    Angular velocity of a bullet and two masses

    As ##P=ccte## we can find final velocity considering a plastic collision ##m_0 . v_0 =(2m+m_0).V## But what about the angular velocity? Because, as the bullet hits the centre of mass of the string, it won't have angular velocity
  44. jisbon

    Calculating electron drift velocity

    Just wanted to check in my workings to see if they are correct (seemed to be too short to me?) Since electrical conductivity is 820 (ohm.m) which is = n*e*(mobility) Mobility =0.17083? And I can simply get drift velocity by multiplying mobility with an electric field (600V/m)? Cheers
  45. L

    Relative velocity in 2 dimensions

    (pw is person to water, pf is person to ferry, fw is ferry to water) I get Vpw = Vpf + Vfw. Therefore Vfw = Vpw + Vpf, which is Vfw = -Vwp + Vpf. I also have that the x component of Vpw is negative. I think I'm getting confused with either the order of the formula or the negative negatives (or...
  46. V

    Velocity of a 1-kg block after it has dropped 0.54 m

    I calculated the system's change in gravitational potential energy through the equation k=mgh. I used this equation twice, once for the 3.5 kg block with k =(3.5)(9.8)(-0.54) and once for the 1.0kg block, k = (9.8)(1.0). I got -18.522J & 5.292. Is the change just -18.522 - 5.292 J...
  47. L

    Initial velocity given time and angle

    From Ball 1 I can can determine it's initial velocity and then maximum height. I'm not sure how this is relevant, as I cannot find a formula using angle, time, height and velocity. I have found h=V(squared) x sin (squared) Theta / 2g and also t=2Vsin Theta/g. These give similar, but different...
  48. TammyTsang

    Engineering Scaling of units for equations of motions

    In the picture, there is a problem where the t is in units of square root(l/g), and V in square root(gl) I am wondering 1. What it means when time is in units other than time? Does it mean that when solving I have to take time/squareroot(l/g) 2. How did they get square root(l/g). Thank you...
  49. M

    Velocity / Acceleration Diagrams of a Mechanism - Piston and a rotating rod

    Summary:: This is a question about finding the acceleration of a point in a mechanism Hi, I have a question about the mechanism shown in the attached picture: Question: We are told that \omega = 6 rad/s and the first part is asking me to find the acceleration of point P on the piston when...
  50. ari-anne

    Finding distance from velocity, force, momentum, mass, and time

    I solved a and b fine, I just don't know where to start c a) i=Ft i=change in p and p=mv so i=90=45v so v=2m/s b) same thing just using the other mass i=90=70v so v=1.3m/s c) v=d/t so 1.3=d/1.5 but that would be d=1.95 and the answer key says d=.96m
Back
Top