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. AN630078

    Finding r of a Jovian-synchronous orbit and escape velocity

    1. The satellite would be in a jovian-synchronous orbit, Rearranging the formula for the orbital period in terms of r, since T^2 is proportional to r^3: T^2=4π^2r^3/GM which becomes r^3=(GM/4π^2) T^2 M(mass of Jupiter)=1.89 x 10^27 G=6.67*10^-11 m^3kg^-1s^-2 T=9 hours and 55 minutes =...
  2. P

    Finding the components of this velocity vector

  3. Leo Liu

    A mistake in the derivation of escape velocity

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  4. K

    Velocity, barrel length and bore volume

    Hello. How does a bullet propell inside a bore? What determine its velocity? I read that a bullet in cal .44 propelled by black powder from a 3” barrel is as powerful as a .25 ACP, however with a longer barrel, the velocity increase significant. With a 8” barrel a .44 black powder bullet is as...
  5. S

    Mechanics: Find the minimum initial velocity and angle of this projectile

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  6. E

    Average velocity in a turbulent flow tube

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  7. F

    Velocity definition and parameter dependence

    Hello Forum, Limiting our discussion to 1D motion, it is clear that the concept of instantaneous velocity is defined as the covered displacement dx divided by the time interval elapsed dt: $$ v = \frac {dx}{dt}$$ However, mathematically, the velocity ##v## can be made to depend on any...
  8. T

    Temperature and Sound Wave Velocity: Exploring the Proportional Relationship

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  9. MichaelTam

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  10. Leo Liu

    Discontinuity of velocity in a problem on mass flow and momentum

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  11. Another

    Velocity in spherical coordinates

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  12. G

    The velocity of the center of the base of a rolling cone

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  13. A

    Velocity due to known acceleration

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  14. J

    Parent needing help with a velocity question including air resistance

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  15. F

    Finding velocity and position of ##a(t)=−\omega^2(C_1\cos\theta+C_2\sin\theta)##

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  16. E

    Orbital and spin angular velocity?

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  17. NovaBlast

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  18. R

    Variable friction on an inclined plane and maximum velocity

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  19. Justinboln

    Calculate the New Velocity and the Velocity of a Pendulum Mass

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  20. LCSphysicist

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  21. B

    Engineering Velocity Ratio, mechanical advantage, Efficiency of a screw jack

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  22. F

    Finding Velocity of Car Slowing Down: v_0-c*(t-t_1)^2/2

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  23. T

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  24. RemotePhysics

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  25. aspodkfpo

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  26. G

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  27. G

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  28. G

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  29. jeffrey

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  30. Sunny Huang

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  31. D

    DV Calculation clarification (rocket booster)

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  32. S

    I Differential form of the velocity equation in a non-standard configuration

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  33. D

    Triangle calculation for the resultant velocity

    Top example- How do I get to 31.7 m/s from 30.8 and 7.7? This is way over my head and need help. Thanks in advance Dean
  34. Rongeet Banerjee

    Root Mean Square Velocity of Gases

    This question came in NEET Exam 2018.Now my first query is that in the question,the mass of one Oxygen molecule is given wrong.Its exactly half it's true value.I don't think anybody has noticed this before because I couldn't find any change in the printed question on so many different books...
  35. Buzz Bloom

    I Formula: velocity of circular orbit wrt Schwartzschild metric

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  36. LCSphysicist

    Motion under a force perpendicular to the velocity

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  37. LCSphysicist

    Prisoner sliding down a rope with minimum velocity

    I thought in this equations f is the man's pull\ f + dm*g = T < 600 Where dm is equal to the mass of the string that pull the up part (15-x) after descending x meters. dm/(15-x) = m/15 And, to the man: W - f = Mx'' I can solve this, and i got ~8m/s Is this right?
  38. K

    Help with understanding this momentum problem

    Solution on the link: https://www.slader.com/textbook/9780321675460-university-physics-13th-edition/269/exercises/12/
  39. dkhurana

    I Four Velocity Vector: why divide by time according to the particle?

    So I understand that time is now part of the four vector, and so dividing delta X by delta t (time according to me), would produce just c as the first dimension of the vector, which gives us no intuition as to how fast time is moving for the observer, so is not useful. I understand why we...
  40. J

    Some Flight Calculations and the Motion of the Earth

    A Problem is posed for a flight from Melbourne to Cairns. Using the formula for rotational speed at latitude - 1) The latitude of Melbourne is approx 38 degrees south with a rotation velocity of 820 miles/hr 2) The latitude of Cairns is approx 17 degrees south with a rotation velocity of 994...
  41. hagopbul

    I Proper Velocity: Intro to Elementary Particles

    Hello : as i read during quarantine introduction to elementary particles by griffth i encounter the following paragraph "When we speak of the "velocity" of a particle (with respect to the labo- ratory), we mean, of course, the distance it travels (measured in the lab frame) divided by the...
  42. JD_PM

    I Understanding how to derive the relativistic-relative velocity formula

    I was studying how to derive the cross-section formula in the CoM frame from Mandl & Shaw QFT's book, and they state the following formula for the relative velocity (I'm going to use Vanhees71's notation though) $$\omega_1 \omega_2 v_{rel} = [(p_1 p_2)^2 - m_1^2 m_2^2]^{1/2} \ \ \ \ (2)$$ Then...
  43. I

    Exploring the Logical/Geometrical Explanation of Escape Velocity

    If you derive the equation for orbital velocity you get \begin{equation} v_{orbit} = \sqrt{\frac{GM}{R}} \end{equation} and for escape velocity you get \begin{equation} v_{escape} = \sqrt{\frac{2GM}{R}}=\sqrt{2}\,v_{orbit} \end{equation} I'm wondering if there is a logical/geometrical...
  44. jamiebean

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    I first calculated initial velocity: √7.09^2+1.07^2=7.17028 acceleration=√7.22^2+2.47^2= 7.63 then i substituted all values into this equation: final velocity=initial velocity + acceleration x time so, final velocity=82.0285 so the magnitude= final velocity-initial velocity= 74.858271 is...
  45. jamiebean

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    I first calculated the velocity v: √2.8^2+6.3^2= 6.8942 then i used it as the final velocity, so final velocity=6.8942 and the initial velocity=0 acceleration=9.8 Then i substituted them into this equation: final velocity=initial velocity + accelerationxtime then time=0.703489843 hence i...
  46. jamiebean

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  47. K

    What is the relationship between velocity and time on this graph?

    This is the graph I was given and the answer options. Since the graph is a straight line moving towards the positive direction I thought that meant it was traveling at a constant speed moving in the positive direction. That ended up being the wrong answer. Can anyone offer insight, I missed each...
  48. F

    Calculating velocity from the position versus time graph

    My answers: a) At points d the instantaneous velocity should be greatest since slope of c-d is greatest I think b) At point e and g instantaneous velocity is 0 c) at points b, c, and f instantaneous velocity is negative. Could you please verify my answers?
  49. A

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  50. G

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