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.

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  1. alejandromeira

    B Time & Limit Velocity (Speed of Light)

    Hello. Today I've thinking about limit velocity and speed of ligth. We know that material particles can't achieve that speed, also when the speed of particles increases your own clock walks slowly. In the particular case of ligth your speed don't move anything. This it a explanation of why...
  2. john-b

    Inconsistency in a Velocity-Time Graph

    Homework Statement We're supposed to convert a position-time graph to a velocity-time graph to an acceleration time graph. These are the values for the position-time graph: Homework Equations m = y2-y1/x2-x1 The Attempt at a Solution I found the slopes for each time which were 5, 8.5, 17...
  3. S

    Position from velocity time graph

    Homework Statement A particle starts from x_0 = 14m at t_0 = 0 and moves with the velocity graph shown What is the object's position at t = 2 s? Homework Equations Area under velocity time graph is the displacement of the particle. The Attempt at a Solution The part that confuses me is where...
  4. S

    Air resistance in projectile motion

    In lower-division physics classes, air resistance is usually ignored to make the mathematics of projectile motion easier to understand. When air resistance is included, it's often stated that at lower velocities, air resistance is proportional to the velocity of the object, Fair ∝ kv At...
  5. J

    Velocity of a particle at time t in a rotating frame

    Imagine two frames one inertial (x,y,z) and the other rotating (x',y',z'), their origins are always coincident. The rotating frame is rotating as seen from the inertial frame with a time-dependent angular velocity ##\boldsymbol{\Omega}(t)=(\Omega_x(t),\Omega_y(t),\Omega_z(t))##. In the rotating...
  6. K

    Finding Initial Velocity v0x for Particle with Non-Constant Acceleration

    Homework Statement Find the initial velocity v0x such that the particle will have the same x-coordinate at time t= 4.07 s as it had at t=0. The acceleration of a particle is given by ax(t)=−2.00 m/s2 +( 3.09 m/s3 )t. Homework Equations v = v0 + a t Δx = ((v+v0)/2)t Δx = v0t + 1/2at^2 v^2 =...
  7. H

    Mass going up an inclined plane with initial velocity Vo

    1. Vo Mass=m 2.So we tried two ways of doing this, one is by taking the y component of the i itial velocity and using that and the other by using the component of its weight parallel to the initial velocity.They give conflicting answers. For the left one it turns out to be t=Vosinθ/g But for...
  8. QuarkDecay

    A Velocity Drifts of proton-muon gas

    When do we use the equations of curvature drift ( ΔΒ⊥Β) V∇B= ±1/2u⊥rL (B x ∇B)/B2 and the general VF= c/q (F x B)/B2? For particles like muons and protons, do they need different equations to calculate a gas' drift velocity, when the gas is made of protons or muons instead of electrons? Am I...
  9. QuarkDecay

    Electron Plasma to Muon/Proton

    Homework Statement Cylinder electron gas with density of ne= 1010 and radius or r=1cm is inside magnetic field of B=104 Gauss. If we change the electron gas with (i) muon gas (ii) proton gas does the Drift Velocity change? Homework Equations [/B] Boltzmann equation of density...
  10. Kairos

    Misinterpretation of the Maxwell velocity distribution?

    I suddenly have a problem with the famous Maxwell velocity distribution. The maximum of this bell-shaped curve is commonly interpreted as the most probable velocity for a particle (see for instance https://en.wikipedia.org/wiki/Maxwell%E2%80%93Boltzmann_distribution: "The most probable speed...
  11. DLeuPel

    Regarding the radius in the orbital velocity

    Would the velocity of a body which is orbiting another body change due to its radius to the center of gravity? If so, why? A body which moves passed a planet and starts orbiting it should have the same velocity it had before ,regarding the fact that it is orbiting a planet. Also, gravity isn’t...
  12. Felipe Lincoln

    Angular velocity of a simple pendulum

    Homework Statement A pendulum with a light rod of length ##l## with a bob of mass ##m## is released from rest at an angle ##\theta_0## to the downward vertical. Find its angular velocity as a function of θ, and the period of small oscillations about the position of stable equilibrium. Write...
  13. P

    Projectile Motion: Initial Velocity Derivation

    Hey guys, I am working on a school project and have fired some water rockets at different angles. I am now trying to compare theoretical results vs experimental results. But I am struggling to produce an accurate mathematical model. I have attached my attempt to this post. It is quite long and...
  14. Mary27

    Runner's Average Velocity: 0.014 m/s

    Homework Statement A runner moves with a velocity of 4.0 m/s due east for 5.0 minutes. The runner then rests for 30 seconds, turns around and heads due west with a velocity of 5.0 m/s for 5 minutes. What is the runner's average velocity for the entire journey from start to finish? Homework...
  15. Paul Lasdivan

    Steam Turbine: Solve for Velocity

    Homework Statement Homework Statement [/B] A steam turbine developed 2372.20 Hp when its inlet condition is 1300 Btu/lb enthalpy and 400 ft/s velocity and steam flow of 200 Btu/min :The exit enthalpy is 800 Btu/min. Find the exit velocity. That is the original problem statement but i think the...
  16. P

    Calculating velocity of a potato

    Hello all! Please note this is my first post and I would love to learn the method of calculating the below question... so that I may retain the knowledge and apply it for further models. First... the question. How can I take the following information... and using existing data find the velocity...
  17. HCverma

    In the circular motion below, what will be the velocity?

    Homework Statement In circular motion what will be the change in velocity if initial velocity and final velocity is 2 m/s? From the left, in the 3rd diagram, if initial velocity and final velocity is 2 m/ s then what is the change in velocity? t = 5 s Homework EquationsThe Attempt at a...
  18. S

    Difference between angular velocity and angular frequency

    I have seen so many questions and confusion about the difference between angular velocity/speed and angular frequency. Usually, answers were always given in the context of uniform circular motion (angular speed) and simple harmonic oscillation (angular frequency), but this is what causes the...
  19. B

    Velocity of a hollow cylinder at the bottom of an incline

    Homework Statement I was looking at the idea that a hollow cylinder will have less velocity than a solid cylinder at the bottom of an incline. I can find the velocity of the hollow and solid cylinder from the following: PE = Translational KE + Rotational KE From that equation I find v and I...
  20. S

    Calculate velocity of the fastest neutron inside a 96Mo nucl

    Homework Statement Calculate the velocity of the fastest neutron in a 96Mo nucleus and, based on this, explain whether or not we are safe to consider such nucleons in a non-relativistic way. Hint: first calculate the Fermi energy. Homework Equations Fermi energy from Fermi gas model...
  21. T

    Liquid ammonia is heated as it flows at a mean velocity of 2

    Homework Statement I've completed this problem and received the below feedback but have gone to a state of complete loss on what to do to amend. Can anyone provide a prompt ? Heat transfer coefficient is correct. But heat transfer rate is wrong - the question says Heat transfer per UNIT...
  22. baldbrain

    River-boat problem (Relative velocity)

    Homework Statement A man wishes to cross a river of width 120 m by a motorboat. His rowing speed in still water (or relative to water) is 3 m/s and his maximum walking speed is 1 m/s. The river flows with a velocity of 4 m/s. (a) Find the path which he should take to reach the point directly...
  23. Felipe Lincoln

    Dependence of force on relative position and velocity

    I read that a force between two bodies can only depend on their relative position and relative velocity. But I can't understand in what is this statement leaning on and what it means.
  24. V

    Find Angular Velocity for Moving Particle Parallel to x-Axis

    Homework Statement A particle is moving parallel to x-axis in the positive direction with velocity v such that at all the instants the y -axis component of its position vector is constant and is equal to 'b'. Find angular velocity about origin. Homework EquationsThe Attempt at a Solution I...
  25. Aleoa

    I Probability density functions for velocity and position

    In the first volume of his lectures (cap. 6-5) Feynman asserts that these 2 can be the PDF of velocity and position of a particle. Under which conditions it's possible to model velocity and position of a particle using these particular PDFs ? ps: Is the "Heisenberg uncertainty principle"...
  26. S

    Can someone help me to calculate the velocity at Stack Tip?

    Homework Statement How can we calculate the velocity at stack tip if the distance of larger diameter is 2.5 m? I think i cannot use the equation of V1A1 = V2A2 because they may have some effect from 2.5 m of distance. Thank you very much. Homework Equations Q1=Q2 The Attempt at a Solution...
  27. navneet9431

    What does the direction of angular velocity indicate?

    Angular velocity is the rate of angular displacement about an axis. Its direction is determined by right hand rule. According to right hand rule, if you hold the axis with your right hand and rotate the fingers in the direction of motion of the rotating body then thumb will point the direction...
  28. Jan Berkhout

    How do I do this trigonometry vector calculation?

    Homework Statement A pilot wishes to fly at maximum speed due north. The plane can fly at 100km/h in still air. A 30km/h wind blows from the south-east. Calculate: a) The direction the plane must head to fly north. b) Its speed relative to the ground. Homework Equations Sine Rule...
  29. S

    MHB Need help with velocity problem that I have no idea how to do

    The velocity of an object is given by the following function defined on a specific interval. Approximate the displacement of the object on the interval by subdiving the interval into the indicated number of subintervals. Use the left endpoint of each subinterval to compute the height of the...
  30. I

    Find the velocity of the rain drops with respect to the man?

    [Mentors' note: No template, as this post was moved from the technical forums] Q. A man is walking on a level road at a speed of 3.0 km/h. Raindrops fall vertically at a speed of 4.0 km/h. Find the velocity of the raindrops with respect to the man, A. The explanation is below: Here I don't...
  31. N

    Work done under constant velocity

    Depending on the answer to this question, I may have others. Consider a one-dimensional ice rink. Rightwards is taken as the +x direction. A box of mass m slides leftward on the surface with a constant velocity v. Two people go to opposite ends of the box and apply equal and opposing forces...
  32. enter

    Negative Velocity or Acceleration

    So, velocity is a vector, right? And vectors can't have negative magnitudes, right? Then why is leftward velocity considered negative in 1D kinematics? It just seems off to me. Same with acceleration, and pretty much _every vector in all of physics._
  33. Gregs6799

    Need to find out the velocity of water

    Homework Statement 3kg/s of fresh water traveling through a pipe of 40 mm, I need to find out the velocity in m/s Homework Equations I have tried the equation: 3 / 40The Attempt at a Solution 3 / 40 = = 0.075m/s But not sure if I have to covert 3kg/s into another value before entering the...
  34. opus

    B Expressing Velocity in Vector Form

    Let me start off by stating a given problem: A baseball is hit, and leaves the bat at a speed of 100 mph and at an angle of 20° from the horizontal. Express this velocity in vector form. So we're given the velocity and the angle at which the ball is hit. The speed corresponds to the vector's...
  35. N

    Common velocity after truck starts pulling a car

    Homework Statement Truck is connected to a car with a rope of given length. The truck starts accelerating with a given acceleration and at some moment starts pulling the car. What is their common velocity just after the car starts moving? Homework Equations I know how to calculate the...
  36. Sandeep T S

    Charge and Velocity: Does Moving Particle Charge Increase?

    Is charge of moving particle increase? Is any experiment done on this,?
  37. C

    Velocity after Free Fall and after Motion down an Incline

    I was doing some conceptual problems quickly before moving on to the numerical stuff when I glanced at this answer given in the solutions manual, and it surprised me: Which object has greater speed at the bottom of its fall, object A of mass m dropped freely from height h or object B of mass m...
  38. hugo_faurand

    B Express Velocity in Formula: Find Answer

    Hello everyone. This is not an homework but I'd like to express velocity ##v## in this formula : $$t' = \frac{t}{\sqrt{1-\frac{v^2}{c^2}}} $$ I've found $$ v^2 = -(\frac{t^2}{t'^2}+1)c^2 $$ I'm sure that is wrong but I don't manage to express ##v## and find the correct answer. Thanks in advance.
  39. F

    I Compton's Effective Velocity and de Broglie == numerology?

    In Compton's 1923 paper, he notes that the scattered wavelength's angular dependence is identical to the Doppler Shift due to an electron moving with the incident wave at an effective velocity: $$\beta = \frac{ h \nu_0 } { h \nu_0 + m_0 c^2 }$$ What's really interesting is that if you calculate...
  40. Osvaldo

    I Circle tangential velocity approaching c

    When a merry go rounds tangential velocity approach c, and horses look closer than when at rest, what is reduced, angular velocity or radius?
  41. Krushnaraj Pandya

    Find the velocity of a rolling disk at time t

    Homework Statement A solid circular disk (m,R) translates with v1 and rotates with angular velocity w1=2v1/R, at t=0. Because of friction, pure rolling starts at time t. the coefficient of friction is C. Find velocity of center of disk at time t Homework Equations 1) for pure rolling v=Rw 2)...
  42. Monsterboy

    How does the velocity of air molecules affect EM waves?

    I would like to know how exactly or if the velocity of air molecules affect the light i.e electromagnetic waves passing through it. Ignoring the effect of pressure and/or temperature differences in the air which might also affect the light (due to changes in refractive index).
  43. P

    Final velocity of two blocks between a spring

    Homework Statement Two blocks have a spring compressed between them, Block A (mass 1kg) and block B (mass 3kg) . The spring has force constant 720 N>m and is initially compressed 0.225 m from its original length. For each block, what is (a) the acceleration just after the blocks are released...
  44. Phylosopher

    Bead on a Helix, angular velocity

    Homework Statement Homework Equations $$\mathcal{L}=T-U$$ $$\omega= \frac{d\phi}{dt}$$ $$I=mr^{2}$$ The Attempt at a Solution My problem is not finding the Lagrangian. But finding the kinetic energy! The translational kinetic energy would obviously be the following: $$K.E...
  45. barryj

    Finding the Velocity of a Mass in Circular Motion

    Homework Statement See attached diagram and statement of problem Homework Equations Conservation of momentum ... mv = MV + mv/2 mv/2 = MV V = mv/(2M) centripetal force...centripetal force equals weight at top of circle. MV^2/L = Mg V^2 = Lg V = (Lg)^.5 The Attempt at a Solution Set V = V...
  46. prakhargupta3301

    Exploring the Relationship Between Velocity and Displacement in Pulley Systems

    Homework Statement Homework Equations xcxcxcxcxcxcxcxcxcxcxc[/B]The Attempt at a Solution My attempt: Let displacement of A be x m, Let displacement of B be y m, and Let displacement of C be z m. Step2: [/B]a+b+c+d=(a+x-y)+(b+x)+c+(d+z) 2x-y=-z Differentiating LHS and RHS components...
  47. I

    How to get average velocity: Vaverage = V1 + V2 / 2?

    Homework Statement How to get Vaverage ( V ) = V1 + V2 / 2? Homework Equations How to get Vaverage ( V ) = V1 + V2 / 2? The Attempt at a Solution As I know Vaverage ( V ) = X2-X1 / t2-t1 = (delta)X / (delta) t
  48. P

    What was the rotational velocity of Earth on Dec 31, 1899

    I ask because time is defined with reference to this day (the SI second is based on a caesium clock is calibrated with reference to the 1952 ephemeris time standard, which was based on a second being 1/86 400th of Jan 0, 1900 (with Jan 0 being Dec 31 of 1899). So... how do I calculate the...
  49. M

    Effect of load and load distance on peak and avg power

    I am trying to create a lever which has mass on one end and i need to lift the lever. A picture showing the lever setup is in this link: https://imgur.com/WeH4oK7 The system is like seesaw ( from -20 degrees to +20 degrees at constant angular velocity for time period 't') The input angular...
  50. I

    I Energy of an Oort Cloud object

    I read that the the energy of an Oort cloud object is approximately zero, as in the potential energy plus the kinetic energy is equal to zero. I was also told that the radius was approximately infinite and the velocity is approximately zero. I understand why the radius is said to be infinite...
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