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. 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?
  2. 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...
  3. 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...
  4. 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...
  5. 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)?
  6. 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 =...
  7. S

    Conceptual problem in average/instantaneous velocity

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  8. L

    Calculate velocity of stopping car

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  9. SpaceIsCool

    Transverse velocity and real/imaginary parts?

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  10. 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...
  11. 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...
  12. Specter

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

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  13. S

    MHB Problem on Tangent and Velocity

    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...
  14. 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...
  15. M

    A Orbit velocity in Schwarzschild metric?

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  16. 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
  17. 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...
  18. 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...
  19. J

    Conservation of Momentum (Explosion Kinematics)

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  20. A

    What Is the Final Velocity of a Particle Under a Time-Dependent Force?

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  21. M

    Drag Force Acting on an Object with Respect to Velocity

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  22. Rahulx084

    Mass Transfer: are both convective mass transfer and eddy diffusion the same?

    I have studied that mass transfer is of two types Molecular mass transfer(diffusion) Eddy diffusion then in later portion of the book I found that there is convective mass transfer too, I wanted to ask if both convective mass transfer and eddy diffusion are same ? I read this equation N_i =...
  23. R

    Find the initial velocity of a water rocket (mass changes)

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  24. G

    Non-constant wave velocity in a ripple tank system

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  25. Cathr

    Question about a derivation: velocity and position

    I started studying Lagrangian mechanics, and the movement equation is like this: d/dt (d/dz') L - d/dz L = 0 if the movement is on the z axis. Now the problem is, let's say L = M(z')2/2 - Mgz. How do we derivate an expression depending of z with respect to z' and also , an expression depending...
  26. T

    Question about Velocity calculation

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  27. H

    I Phase and group velocity for a free particle

    Why for the free particle, the group velocity and phase velocity are not the same while we have only one wave? What is the envelope here?
  28. TachyonLord

    The order of calculating velocity and position alters the solution?

    So I tried solving the differential equation for a spring - mass system using Euler's Algorithm in Python. The equation being d2x/dt2= -4π2x (The equation was obtained by Dimensional Analysis) here x and t are both dimensionless equivalents of position...
  29. X

    I Understanding the Relative Velocity Paradox

    Hi! I'm an utter novice at physics, so please bear with me if I ask a foolish question. I just learned that velocities don't purely add: 2m/s + 2m/s does not equal 4m/s, but something like 3.9999999...9 m/s, and so on. Something to do with the upper limit of c. Logic makes me assume that this...
  30. J

    Minimum deceleration to prevent a collision

    Homework Statement At a given time ##t=0##, a car 1 moving with constant velocity ##v_{1}## breaks with constant deceleration ##d##. Another car 2 at a distance ##L## behind car 1 and traveling with constant acceleration ##a_{2}## and velocity ##v_{2}## at ##t=0## brakes immediately as soon as...
  31. artworkmonkey

    Sun question: Determine the velocity of the gas

    Homework Statement From near to the center of the solar disc, Fe I line emission from point X shows a spectral line with components 666.823, 666.830 and 666.837 nm, around the rest wavelength of 666.800 nm. The central component is not as bright as those at the longer and shorter wavelengths...
  32. WhiteWolf98

    Rigid Bodies/ Angular Velocity

    Homework Statement Homework Equations ##v=\omega r## The Attempt at a Solution So, using the equation, one can work out the velocity at point ##B##. ##v_B=\omega_{AB} \cdot r_B## ##v_B=6(0.4)=2.4~ ms^{-1}##I then tried working out the angular velocity at point ##C## using the instantaneous...
  33. J

    MHB Terminal Velocity Calculation: Understanding Forces at Play

    Hi All, I am struggling with the question (attached) and was hoping to get some guidance and explanation on how to solve it. I`m thinking that it is force down is equal to force up? But I could be wrong. Any help greatly appreciated. Regards, James
  34. Raphael30

    Velocity of a falling folded rope and reaction force

    Homework Statement A rope of length L and mass m is attached to the ceiling and folded at mid length. The free end of the rope is held against the ceiling, then dropped at time t=0. a) Calculate the velocity of the free end as a function of y, its distance from the ceiling. b) Calculate R...
  35. S

    Velocity of image in plane mirror

    Homework Statement A mirror is moving to the right with a velocity 15 m/s, and an object is moving to the right with a speed of 5m/s. All speeds are wrt ground. Find the velocity of image wrt ground. Homework EquationsThe Attempt at a Solution I present to you two probable solutions: 1) Using...
  36. Viona

    Average Velocity of gas molecules calculated with a Boltzmann distribution

    Hello What is the meaning of the average velocity of gas molecules calculated by Boltzmann distribution (in kinetic theory of gases)? Does all molecules have the same average velocity?
  37. R

    B Does time dilation prove the existence of an absolute zero velocity?

    You may think you've seen this before, since I've seen similar discussions in the archives of this, but I think I've distilled the thoughts down to a couple of facts that contradict the common beliefs regarding relativity. Let me preface this with a basic observation: Lorenz invariance does not...
  38. N

    B Velocity Addition Q: Ball Thrown from Moving Ship?

    Suppose a spaceship is flying past me, an observer on earth, at .86c. A traveler on the ship has a ball which is attached to a string which is 100 feet long in the ship frame. The traveler grabs the string and throws the ball out of the front window of the ship at a speed of 100 feet per second...
  39. S

    I Escape Velocity: Newtonian vs Relativistic

    Hi, Do we obtain the same escape velocity equation: Ve = sqrt(2GM/r) using both Newtonian and Relativistic approach?
  40. J

    Acceleration of a particle on a parabola

    Homework Statement A particle moves along a parabola on the x-y plane with equation ##y^{2}=2px## with constant speed ##1000m/s##.What is the magnitude of its acceleration? Homework Equations Parametric equations ##\vec{r}=(b^{2}t^{2}/(2p),bt)##. The Attempt at a Solution...
  41. J

    Determine the period of small oscillations

    Homework Statement Two balls of mass m are attached to ends of two, weigthless metal rods (lengths l1 and l2). They are connected by another metal bar. Determine period of small oscillations of the system Homework Equations Ek=mv2/2 v=dx/dt Conversation of energy 2πsqrt(M/k) The Attempt at a...
  42. nmsurobert

    B What is the Correct Formula for Calculating the Velocity of Saturn's Rings?

    I'm setting up a lab for my class and I've found this equation, but I can't find where a constant value is coming from. "...the speed of rotation of the rings is related to their radius (from the center of Saturn) by the following equation: where R is the distance from the center of Saturn...
  43. E

    Phase relation between strain and particle velocity

    I'm trying to understand the following derivation. Starting with the one-dimensional equation for a traveling wave ##u = u_0 \exp{[j(\omega t - \beta z)]}## the goal is to derive the phase relation between strain and velocity. The author first derives the relationship between strain and particle...
  44. cookiemnstr510510

    Solve Magnetic Field Homework: Find Velocity of Metal Strip

    Homework Statement A metal strip 6.5cm long, 0.88cm wide, and 0.76cm thick moves with constant velocity, magnitude v along positive y-axis, through a magnetic field, B=1.2mT along positive z-axis. A potential difference of 3.9x10^-6V is measured between points x1 and x2 (as shown in...
  45. J

    Angular Velocity Problem — a Piston and a Crank

    Homework Statement I have been set this question and I am struggling with parts b and c. I think I am nearly there but can't quite get over the line. Please could someone give me a nudge in the right direction. [/B] 1. (a) For the mechanism shown in FIGURE 1 determine for the angle θ = 45°: (i)...
  46. T

    A How much does peculiar velocity affect distance measurement?

    I'm a PhD student who's taken GR, so I have studied gravity and cosmology, and we have the underlying assumption of homogeneity and isotropy, but since this assumption comes from how we've calculated the distribution of galaxies in the visible universe I want to make sure I really understand it...
  47. H

    Calculating the final velocity of a simple electric train

    I am currently in grade 12, and for a physics project (a huge project, which gets assigned to you at the start of the semester and needs to be completed just before exams. You think up your project, make a proposal for it and you prove your hypothesis to be right after a presentation and lab...
  48. T

    Time of Fall in triangular and rectangular frame

    Homework Statement This question is actually two question. We have two hollow frames - one is rectangular and another is triangular. the rectangle is rotated and fixated such that the angles in shape are ##\alpha , \beta = 90 - \alpha## and the angle of triangle is ##\alpha##. We have two balls...
  49. M

    Change in momentum when given the speed (not the velocity).

    1. The problem statement. A tennis ball of mass m moving horizontally with speed u strikes a vertical tennis racket. The ball bounces back with horizontal speed v. Homework Equations p = mv The Attempt at a Solution My answer was m(v-u), meaning the final momentum (mv) subtracted from the...
  50. J

    What velocity does a train need to go up and down the hill

    Homework Statement There is a train of length d and speed v. It is heading towards a hill with height h and length of each side l. What velocity requirement must be met so that the train can go up and down the hill? Homework Equations Ek=m⋅v2/2 Ep=m⋅g⋅h The Attempt at a Solution I'm basically...
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