Velocity Definition and 1000 Threads

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. EEristavi

    Motion in 2 Dimensions & Relative velocity

    Homework Statement The water in a river flows uniformly at a constant speed of 2.50 m/s between parallel banks 80.0 m apart. You are to deliver a package across the river, but you can swim only at 1.50 m/s. (c) If you choose to minimize the distance downstream that the river carries you, in...
  2. F

    Blood flow velocity via Doppler effect

    Homework Statement A Doppler flow meter is used to measure the speed of red blood cells. The frequency of the apparatus is f = 12 MHz. The sensor in the apparatus measure 1.8 kHz beats between the emitted frequency and the frequency of the ultrasound reflected back by the blood cells. The speed...
  3. J

    Finding recoil velocity of an object during a collision

    Hello. I recently began this problem, but the site I'm working this problem on isn't showing me whether the answer is correct or not. Can someone please check my work and just verify that it's correct or state if it isn't and why? 1. Homework Statement A cosmic-ray photon (with mass m...
  4. MedEx

    Find the Velocity given Magnetic field and Magnetic Force

    Homework Statement A proton moves through a uniform magnetic field given by B=(13.7i−22.9j+23.5k) mT. at time t1 v=(vxi +vyj+1.68k)km/s and the magnetic force is given by F= (4.22e-17i + 2.52e-17j). What are vx and vy Homework Equations F=q(v x B) The Attempt at a Solution First I converted...
  5. Yasin

    Maximum Angular Velocity of a quarter circle

    Homework Statement Finding the general formula for max angular velocity ( answers say 0.839*(g/b)) but I do not understand how Homework Equations 0.839*(g/b) The Attempt at a Solution
  6. Z

    When would a rocket return that was at escape velocity

    we all know escape velocity is a velocity in which a body can escape orbit around the Earth and fly off into space. this needs to happen in space our just out of our atmosphere, due to drag that could bring an object back into orbit and cause it's velocity to degrade to a point where it would...
  7. DeathByKugelBlitz

    Kinetic energy and velocity of electron after compton scatte

    Homework Statement A photon with an initial wavelength of 0.1120 nm collides with a free electron that is initially at rest. After the collision the wavelength is 0.1140 nm . a) What is the kinetic energy of the electron after the collision? b) What is its speed? c) If the electron is...
  8. matai

    Integral for the linear speed of the Earth

    I need to make an integral to fine the speed of the earth. Say the radius is 6378137 meters. How would I account for things closer to the axis that have a radius of 0.0001 meters? I don't think I can just take the speed at the radius. So I found that the Earth rotates at 6.963448857E-4 revs/min...
  9. C

    I What does the wavenumber in a group velocity represent?

    I'm trying to wrap my head around the dispersion relation ##\omega(k)##. I understand how you can construct a wavepacket by combining multiple traveling waves of different wavelengths. I can then calculate the phase and group velocities of this wavepacket: \begin{align*} v_p &=...
  10. G

    Acceleration and Velocity: Understanding the Relationship

    Is there a correlation between acceleration and velocity? If acceleration is rising will the velocity also rise?
  11. M

    Rigid Body Rotation relative velocity question

    This is a question about the concepts behind rigid body rotation when we use relative velocity. In general, let us say that we have a rigid body and on it are two points, A and B, which are moving with velocities vA and vB respectively. These velocities are in random directions. The theory...
  12. Isolde Wilde

    Are angular & vertical velocity the same if the objects are connected

    think of a engine. it has a flywheel and a rod connected to it. a string had been totally wrapped around the rod and a mass is hanged from the very end of the rod. the system is in equilibrium. but as the engine starts to rotate, the rod with rotate as well and cause the hanged object to go...
  13. hyksos

    I Imaging galaxies receding at a velocity that exceeds c?

    There are galaxies that are so far away that metric expansion causes them to have a co-moving recessional velocity that exceeds the speed of light. However, those galaxies are also so far away that the time it took the light to reach us was itself billions of years in the passage of its journey...
  14. T

    How come "terminal velocity" and "final velocity" are different?

    Homework Statement Someone shot the bullet perpendicular to the ground. And there is air resistance. Velocity of bullet is v^2 = Ae^(-2kx)-g/k upward v^2 = g/k-Be^(2kx) downward A,B is constant, g is a gravitational acceleration, k = c2/m , c2 is a resistance constant, m is a mass...
  15. T

    Why do we need the hyperbolic excess velocity?

    $$V_{HE}=\sqrt{\frac{\mu}{a}}$$ What is the rationale for this formula when we can determine the change in velocity from Earth's orbit to transfer orbit using the vis-viva equation? Likewise, what is the use of defining the radius for the sphere of influence for interplanetary transfer...
  16. S

    Kinematic problem: velocity and stuff

    1. A stone is thrown vertically downwards from the observation deck of the CN Tower, 400 m above the ground, with a velocity of 12 m/s [down]. A) How long will it take the stone to reach the ground ? B) How fast will it be going when it hits the ground ? I just got into physics, so I’m not...
  17. Storm Savage

    Is there a terminal velocity upwards?

    We are all familiar with the concept of terminal velocity due to air friction in the direction towards the earth, but what about the other direction? Given enough applied force, is it possible to experience a terminal velocity upwards?
  18. W

    MHB Advanced Functions Average vs. Instantaneous velocity

    What do the average velocities on the very short time intervals [2,2.01] and [1.99,2] approximate? What relationship does this suggest exist between a velocity on an interval [a,b] and a velocity near t=a+b/2 for this type of polynomial?
  19. SchroedingersLion

    Equivalence of msd and velocity autocorrelation

    Greetings, I am searching for an explanation that connects the mean squared displacement in an ensemble of particles to the velocity autocorrelation functions. I know that they are connected since both of them can be used to calculate the diffusion constant. But I do not find a mathematical...
  20. D

    Determine the angular velocity as a function of the angle

    Homework Statement A solid body begins to rotate around a fixed axis with angular acceleration ##\beta=\beta_0\cosφ##, where ##\beta_0## is a constant vector, ##φ##, is the angle of rotation of the body from initial position. Determine the angular velocity of this body as a function of the...
  21. F

    Kinetic theory of gases and velocity correlations

    I have been reading up on the kinetic theory of gases, and I'm unsure whether I have correctly understood why particle velocities become correlated after colliding. Is it because during the collision they exchange momentum and thus their velocities (and hence trajectories) are altered in a...
  22. Lapse

    What is the final V in the vertical direction?

    Homework Statement Homework Equations Vy2 = Vyo2 + 2ayt y = 1/2(Vyo + Vy)t The Attempt at a Solution So I have "solved" this problem with both the equations above. Using the Vy2 equation I get the result of 32.83m/s. Using the other equation I get a result of zero, because Δy = (0 - 55) =...
  23. Lapse

    What is the expression for the velocity of the Car in Vector

    Homework Statement Homework Equations v = I + j + k v = d/t The Attempt at a Solution I thought the answer was as simple as: v = 63i + 0j + 0k, since the car only has motion in one direction... ...but I got it wrong, so clearly I'm missing something here.
  24. D

    1D Angular Motion with different velocity stages

    Homework Statement I am solving a kinematic problem, where I have a link that is attached to a rotational joint. I need to find the position of the joint for t=0..8, and I need to do it for every 0.01s. The problem comes from the fact that I have three stages for the velocity, during t = 0..0.1...
  25. P

    Free fall velocity and distance

    Homework Statement A 0.1 kg nut is thrown by a squirrel off of the top of a 10 m tall tree. It is thrown with an initial upward velocity of 4 m/s and an initial horizontal velocity of 3 m/s. a) How long till it reaches the top of its arc? b) From the top of its arc how long till it reaches the...
  26. L

    Question About the Escape Velocity from Different Mass Planets

    Hi! I have a question about escape velocity. If a planet is bigger and have a greater escape velocity than another planet. Do this effect the density of the bigger planet in any way? Or do we have to know the mass of the bigger planet to know if the density is larger or lower for this planet?
  27. liroj

    Terminal velocity of two balls with different masses

    Two objects of the same shape (say balls) fall through the Earth's atmosphere. For simplification, let's say that the air density is the same (some average sea level value) despite altitude change. One ball has considerably bigger mass than the other, but besides that, they're the same. Will...
  28. Rahulx084

    Shear stress direction and the velocity gradient

    1)In a flowing fluid in laminar fashion we know that it flows in planes which slides over each other, Let's take a fluid element (cylindrical) in a pipe(Radius=R) the resistive force is (stress)(cross section area of cylinder with radius 'r') acting in backward direction, now if I take Flow...
  29. Charge

    Adding Vectors to Find Velocity

    Problem: Dr. L and his cat Kepler are coming home from fishing. They ended their trip on the south bank of a river, directly across a 1200 m wide river, from where Caroline was going to pick them up on the north bank. They are in identical boats that can travel at 4 m/s (Vb). The river is...
  30. redtree

    I Legendre Transform: Momentum & Velocity

    I apologize for the simplicity of the question. I have been reading a paper on the Legendre transform (https://arxiv.org/pdf/0806.1147.pdf), and I am not understanding a particular step in the discussion. In the paper, Equation 16, where ##\mathcal{H} = \sqrt{\vec{p}^2 + m^2} ##...
  31. J

    Why Does Acceleration Decrease When Velocity Increases in SHM?

    When a mass is in SHM, and is moving towards equilibrium point, its velocity starts to increase but why does acceleration decreases? What is the gradient when velocity is increasing and when it is at maximum? Thanks a lot!
  32. P

    Equation for falling objects that includes terminal velocity

    if an objects terminal velocity in air is 18m/second, when what would be an equation that describes its velocity from t0?
  33. Charlie Cheap

    Automotive Velocity vs Volume in the intake

    I have a 1973 Ford 200" six to replace the same size engine in my 1965 Mustang. The .060" overbore in the original engine is too much making the walls too thin. It works but hard starting when hot, so I got a newer 200. The intake is cast with the head so the intake manifold can be a problem...
  34. AgNO3

    Find the magnitude of this velocity - SHM problem

    Homework Statement Two rubber pads are affixed at the bottom of a box and the assembly thus formed is placed on a uniform slope of inclination 0.5 degrees. Coeff of friction is 0.60 between the pads and the plane. Two electric motors installed in the box can make the pads move back and forth...
  35. ashhlyn

    Finding the expression for the x-component of velocity (vectors?)

    Homework Statement a particle's position is the vector r=(ct^2-2dt^3)i+(4ct^2-dt^3)j where c and d are positive constants. find the expression for the x-component of the velocity (for time t>0) when the particle is moving in the x-direction. you should express your answer in terms of variables...
  36. arda

    I Why particles have group velocity?

    I just confused about it.Why can't we discribe a particle just one wave function instead of wave packet(group of waves with different phase velocities)?
  37. A

    Siphon pressure and velocity problem

    Homework Statement Homework Equations Bernoulli equation. Continuity equation The Attempt at a Solution Area of pipe is constant, so v_a = v_b = v_c = v_d.[/B] Using point on water surface and point D. Point on water surface: z = 8, v = 0, P = 0 (P_atm) Point D: z = -2, P = 0 (P_atm) v =...
  38. S

    Conceptual problem in average/instantaneous velocity

    Homework Statement I am having a bit of confusion regarding this: When you write dr/dt (rate of change of position vector with time, sorry I don't know how to use LATEX), do you mean instantaneous or average velocity? As we are considering a very small time interval, I guess it is...
  39. L

    Calculate velocity of stopping car

    Homework Statement A car moving at 20m/s starts decelerating, travels distance d, and stops. Find the car’s velocity at distance d/2. Homework EquationsThe Attempt at a Solution my brain is fried. I feel like I’m missing something obvious but I just don’t get it.
  40. SpaceIsCool

    Transverse velocity and real/imaginary parts?

    Homework Statement The transverse velocity of the particle in Sections 2.5 and 2.7 is contained in (2.77), since By taking the real and imaginary parts, find expressions for v_x and v_y separately. Based on these expressions describe the time dependence of the transverse velocity. Homework...
  41. SpaceIsCool

    Can This Differential Equation Be Solved by Separation of Variables?

    Homework Statement We solved the differential equation (2.29), , for the velocity of an object falling through air, by inspection---a most respectable way of solving differential equations. Nevertheless, one would sometimes like a more systematic method, and here is one. Rewrite the equation...
  42. A

    Flight Path Angle and Velocity During Atmospheric Re-entry

    A space vehicle enters the sensible atmosphere of the Earth (300,000 ft) with a velocity of 25,000 ft/sec at a flight-path angle of -60 degrees. What is its velocity and flight-path angle at an altitude of 100 nautical miles during descent? (Assuming no drag or perturbations, two body orbital...
  43. Specter

    Velocity of the ball when it hits the ground, limits?

    Homework Statement [/B] The path of a baseball relative to the ground can be modeled by the function ##d(t)=−t^2+8t+1## , where d(t)represents the height of the ball in metres, and t represents time in seconds. What is the speed of the ball when it hits the ground? Homework EquationsThe...
  44. S

    MHB How Do You Solve Problems on Tangent and Velocity for a Sliding Ladder?

    Hi guys! I had a question on the bolded sections below and wondered how to solve this in a step by step solution. I already have the answers, but don't know how to solve it. I will show the whole problem so that any content needed is available for sections e and d which I am stuck on. Thanks! A...
  45. opus

    Integrating Velocity: Questions on Displacement & Position

    Please see the attached image which are of my notes. In integrating acceleration, I have no confusions. But I have a specific question about integrating velocity. When we integrate velocity, do we get the displacement of ##x##, or do we get it's position at a certain time? I want to say it's...
  46. M

    A Orbit velocity in Schwarzschild metric?

    Hi, I'm trying to deduce orbit velocity of a particle with mass from Schwarzschild metric. I know for Newtonian gravity it is: $$v^2=GM\left(\frac{2}{r}-\frac{1}{a}\right)$$ The so called vis-viva equation. Where ##a## is the length of the semi-major axis of the orbit. For Schwarzschild metric...
  47. J

    Torque and tangential velocity

    What is the moment of inertia and what relationship does it have to do with the torque. I have advanced physics
  48. H

    Why is the velocity of a jump on Mars the same as on Earth?

    Homework Statement Good evening, I have a homework where the question is "How high will person jump on Mars?" Homework Equations v2 = 2.amars.h1 V2 = 2.g.h2 The Attempt at a Solution I know everything to solve it. I can solve it by h1 / h2 . In this created equation the only unknown is h1...
  49. M

    Collision finding final velocity

    1. A baseball of mass 0.30kg is pitched at 70m/s (fwd) at a batter. The ball knocks the stationary 1.7kg ball out of the batters hands and the ball rebounds at 48m/s (backwards). What is the final velocity of the bat as it leaves the batters hand? variables m1 = 0.30 vi= 70 vf = -48 m2= 1.7...
  50. J

    Conservation of Momentum (Explosion Kinematics)

    Homework Statement [/B] A 3200 kg space vehicle (including a launchable lifeboat) is traveling with a velocity of 300 m/s in a straight trajectory [East]. The lifeboat (200 kg) is fired at a speed of 1000 m/s [N of original trajectory]. a) After firing it is found that the horizontal...
Back
Top