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. T

    Angular Velocity: Pulley and belt system

    So far I have: The velocity of the belt will be the same for pully A and D, so we can calculate the angular velocity of pulley D: ## V_A = V_B ## ## \omega_A r_A = \omega_D r_D ## ## ((20*3)+40)(0.075) = \omega_D (0.025) ## ## \omega_D = 300 Rad/s ## My next step was to determine the angular...
  2. mncyapntsi

    1-D Motion, calculating final velocity

    Hello! I have done this problem : vf^2 = (4.0x10^5)^2 + 2(6.0x10^12)(5x10^-3) so vf= sqrt((4.0x10^5)^2 + 2(6.0x10^12)(5x10^-3)) I get vf = 4.7 x 10^5 m/s However, the textbook solutions says vf = 8.7x10^5 m/s. Where did I go wrong? Thank you for any help! :)
  3. U

    Velocity at a reservoir (Bernoulli's equation)

    Hi there, I am solving a problem which requires me to use Bernoulli's equation and I have across a hint that says that "velocity at the reservoir is negligible because the reservoir is large" and I do not understand what that means exactly. How is velocity at a reservoir negligible?
  4. U

    Pebble accelerated by the wind with a starting velocity

    I first used differentials to find an equation for the displacement. $$6.0t^2+5.0t=13$$ and using the quadratic formula I got time ##t=1.1## I then got ##V_x## from ##6.0t+5.0=v_x=11.6## and ##V_y## from ##7.0t=v_y=7.7## The I got v from ##V=\sqrt {V_x^2 + Vy^2} ## $$\sqrt {11.6^2 + 7.7^2}...
  5. P

    I Tangential velocity of an object rotating around a rotating axis

    Hi all, It has been some time since I've done physics. I wish to model some projectile motion of a lure being cast from a fishing rod. The setup is very similar to that of a trebuchet. The fishing rod - we'll assume a perfectly rigid beam - is rotating about a fixed axis. I can calculate...
  6. N

    Engineering Find the velocity and angular velocity of the rod and point

    Hi everyone :)! I resolve this problem with components method and trigonometry method. My results with components method its okay, but i can´t obtain the correct VE velocity. Im sure that the problem its in the angles, but i don't know how to fix it. The correct answers: -Angular velocity...
  7. C

    Show the velocity graph of a 4.7 kg object as it moves along the x-axis

    If force= m•a would the answer just be the y-axis • 4.7 at the specific time such as A) 4.7 • 6 = 28.2? B) 4.7 • 12= 56.4 C) 4.7 • 3 = 14.1
  8. ronald_hinh

    I Time Dilation: Gravitational & Velocity Effects Explained

    I'm trying to understand what the time dilation looks like when moving through space and then approaching a planet's gravity field. So I have the broad understanding that if you are moving near the speed of light in a spaceship, your clock ticks normal but the clocks on other stationary objects...
  9. L

    Determine the velocity of two balls after the first collides with a lever

    In the figure below Ball 2(B2) is hanging and attached to a square lever. B1 drop from gravity and hit the lever as shown. Calculate velocity of B1 and B2 with gravity influence right after collision. The mass of B1 and B2 is identical. Using energy equation E1=E2, therefore VB2 final = VB1...
  10. Narayanan KR

    A Different Way to Achieve Electron Velocity Modulation in a Klystron

    Please Notice That the Toroid Coil is Outside the Discharge Tube and yet able to influence electrons moving inside the Tube.
  11. mncyapntsi

    Intro Physics homework help - distance and velocity

    I have tried this problem over 4 times and keep getting the exact same answer, which is incorrect. Could someone please help by pointing out what I did wrong, or letting me know if I am actually on the completely wrong path? Thanks! Have a wonderful day :)
  12. N

    Find the angular velocity of this linkage

    Hi! everyone! ;) I have a problem with the development of this problem. I need to resolve it with 2 procedures: trigonometry and instant centers. My advance can be see in the next image: The instant centers procediment its (1) up and trigonometry procediment its (2) down. I know that the...
  13. L

    Finding The magnitude of the velocity

    i have tried V=Vi - (g*t) with an answer equals to 4 as well as d=Vi(t) + 1/2 a t^2 with an answer equals to 19 my final asnwer was 1.43 and it was still wrong i used formula a=v/t v=14 t=10 i divided 14/10 to get 1.4
  14. R

    Finding the velocity of a car in a different frame of reference

    Here's what I did so far. The velocity of the first car is ##v = v_0 +at## Frame of reference S = the road Frame of reference S' = the second car thus, v' is the speed of the first car in the frame of reference S' and v the speed in the frame of reference S. Here's what make me doubt. The...
  15. C

    I Is acceleration a more absolute/fundamental quantity in the universe?

    Was wondering if acceleration seems to be a more fundamental property/quantity in the universe as compared to velocity or distance because acceleration can be defined in more absolute terms in a frame depending on the forces acting inside that reference frame. Considering a very simple example...
  16. L

    I Relativistic Force & Velocity Relation to Acceleration

    According to this link here https://en.wikipedia.org/wiki/Relativistic_mechanics#Force , we can inverse the relation of force in terms of velocity and acceleration: $$ \mathbf{F} = \frac{m\gamma^3}{c^2}(\mathbf{v} \cdot \mathbf{a})\mathbf{v} + m\gamma\mathbf{a} $$ to get: $$ \mathbf{a} =...
  17. Istiak

    Find velocity with vector or without vector

    At the moment he wrote that ##\frac{1}{2}mv_2^2=\frac{1}{2}m(-\dot{y}+\dot{x})^2## But, I know from vector ##v_2=\sqrt{(-\dot{y})^2+(\dot{x})^2}##. At first I (he) found that ##v_2=-\dot{y}+\dot{x}##. But, when thinking of simple velocity in ##x## and ##y## coordinate then I get...
  18. L

    Tangential velocity of rotating rod

    1) ##LT\sin(\frac{\pi}{2}-\theta)-\frac{L}{2}mg\sin\theta=0\Rightarrow T=\frac{mg}{2}\tan\theta##. ##N_{x}-T=0, N_{y}-mg=0\Rightarrow N=\sqrt{N_x ^2+N_y ^2}=mg\sqrt{(\frac{\tan\theta}{2})^2 +1}## 2) ##E_{k_{fin}}=mg\frac{L}{2}[1+\cos\theta]## 3)...
  19. A

    Propagation Wave Expressions and Wave Velocity

    Hello everyone, I would really appreciate some help on the following problem on plane waves and propagation. Not too sure if my attempt at writing the propagation wave expressions are correct, and how to handle the arbitrary function f(u). For the velocity, the wavelength is not specified, so is...
  20. G

    I Velocity in Relativity: Theoretical Analysis of Multi-Dimensional Universes

    There are several theoretical analyses of 2 dimensional or of multi-dimensional universes. Now, we live in a special universe that follows Newton's first law (A body at rest or a body in motion shall continue to be at rest or in motion till acted upon by an external force), and consequently...
  21. Istiak

    Calculating Velocity when Stuntman Jumps from 1.25m Height

    > >A stuntman jumped from $1.25 \ \text{m}$ height and, landed at distance $10 \ \text{m}$. Find velocity when he jumped. (Take $\text{g}=10 \ ms^{-2}$) I had solved it following way. $$h=\frac{1}{2}gt^2$$ $$=>1.25=5\cdot t^2$$ $$=>t=\frac{1}{2}$$ And, $$s=vt$$ $$v=\frac{s}{t}$$ $$=\frac{10 \...
  22. A

    B Why Is Initial Velocity Not Always Zero?

    There is something I don't understand. Isn't every object, if thrown, the initial velocity is zero? Please take a look at below example. Why the initial velocity in the below example is 98 ms^-1? Please explain. I also would like to ask what textbook contain a lot of basic physics example for...
  23. Huzaifa

    B Acceleration of Moving Particles: Explained

    I am not able to understand the following paragraph from my Physics textbook;
  24. Marwan1303

    I Pipe Air Blowing - Exit Velocity of Air

    Suppose an isolated pipeline of known dimensions is being filled with air from the atmosphere (via a compressor) to a gauge pressure P1=2barg. A rupture disc at one end of the pipeline blows at this pressure, and the air inside the pressurized pipeline is released to the atmosphere. The rupture...
  25. karush

    MHB 1.2.1 propelled vertically upward with an initial velocity of 20 meters per second.

    $\tiny{1.2.1}$ An object is propelled vertically upward with an initial velocity of 20 meters per second. The distance s (in meters) of the object from the ground after t seconds is $s=-4.9t^2+20t$ (a) When will the object be 15 meters above the ground? $15=-4.9t^2+20 \implies -4.9t^2 =-5$ ok...
  26. WMDhamnekar

    MHB Proof of known velocity of wind

    My attempt to answer this question: Let the actual velocity of wind is $\vec{v}=x\hat{i} + y\hat{j}$ where $\hat{i}$ and $\hat{j} $ represents velocities of 1KM per hour towards east and north respectively. As the person is going northeast with a velocity of 6KM/hr, his actual velocity is $...
  27. baby_1

    Phase velocity in oblique Angle propagation (Plane wave)

    Hello, Regarding the wave oblique angle propagation and based on Balanis "Advanced engineering Electromagnetic" book on page 136 ( it has been attached) I need to know why the phase velocity in x direction is not important to keep in step with a constant phase plane( Just equation 4-23). I...
  28. WMDhamnekar

    MHB Understanding Velocity and Acceleration of a Moving Particle

    A particle moves so that its position vector is given by $\vec{r}=\cos{(\omega t)}\hat{i} + \sin{(\omega t)}\hat{j}$. Show that the velocity $\vec{v}$ of the particle is perpendicular to $\vec{r}$ and $\vec{r} \times \vec{v}$ is a constant vector. How to answer this question?
  29. WMDhamnekar

    MHB Question on velocity and acceleration

    How to answer this question? Any math help, hint, or even correct answer will be accepted.
  30. WMDhamnekar

    MHB Velocity and acceleration vectors and their magnitudes

    How to answer this question? I am working on this question. Any math help, hint or even correct answer will be accepted.
  31. Ashshahril

    How to Visualize a 4 vector (e.g. a velocity)?

    Velocity is a 4-vector which has 3 space dimensions and 1 time dimension. It's space parts will be directed at the 3 space directions and time parts will be directed at the time dimension (But it is inverse. So, will it point at the inverse direction?). How can someone Visualize it? How they...
  32. Huzaifa

    B Average Speed vs. Velocity: Explained

    Though average speed over a finite interval of time is greater or equal to the magnitude of the average velocity, Instantaneous speed at an instant is equal to the magnitude of the instantaneous velocity at that instant. Why so?
  33. E

    Can you use speed and velocity interchangeably?

  34. E

    When an object is accelerating, does speed, velocity, or force change?

    qn3: why is statement 2 the only answer? isn't speed one of the factors in velocity too? then shouldn't statement 1 be true too?
  35. K

    A Can high air velocity in vacuum system create "freezing" of the pipe?

    Hi folks, very simple question, but have not been able to find an answer: Assume a vacuum pump pulls air through a pipe. Also assume that within the pipe run, there is an area with reduced cross section, creating a temporary increase in air velocity. Also assume the air is very moist, and is at...
  36. E

    Vorticity and Curl of Velocity

    This is not homework. I'm studying fluid mechanics/dynamics in the heart/blood vessels and I just want to understand this, so I can have a better appreciation for it's clinical relevance. I'm more of biology/biochem type of person so this has been a bit of challenge. I have basic physics course...
  37. WMDhamnekar

    MHB What is the velocity vector after a pinball bounces off a baffle?

    Hi, A pinball moving in a plane with velocity s bounces (in a purely elastic impact) from a baffle whose endpoints are p and q. What is the velocity vector after the bounce? I don't understand how to answer this question? Any math help, hint or even correct answer will be accepted?
  38. B

    What is the perceived relative velocity of these two motorcycles?

    I tried to project one on top of another but I know that's incorrect since I don't know how of do this.
  39. Andy Resnick

    I Apparent angular velocity (inclined orbit)?

    Here's the problem setup, my student and I are stuck. A disk is rotating at constant angular velocity ω, and we are watching a point on the rim, parameterized by the angular position θ, move. Because we are observing the motion from an inclination angle Ψ, we do not always observe the...
  40. S

    Calculation of orbital velocity -- Geometrical solution

    Hello, I would like to calculate the orbital velocity using the geometrical way of reasoning. But I have a hard time to understand and apply some basics into my calculations. The reasoning is pretty simple. After some time: dt ,the particle travels the distance: Vtot1 * dt = R*sinθ (see the...
  41. S

    Why is the integrated velocity times change in velocity zero?

    So consider a subject system, a galaxy, with stars in it. This galaxy is passed by another object, the perturber. When the interaction is fast, we call this interaction a high-speed encounter. Now we consider that the interaction is really fast. This means that during the interaction, the...
  42. S

    Hurricane forces — Comparing the force from a 60 mph wind to a 120 mph wind

    The marker wrote that the answer is 4 and it's because m and v double. I don't understand how m doubles??
  43. B

    Existential dilemma on angular velocity of a complex rigid body

    I assumed the angular velocity of the center of mass of the two discs about z axis to be w1 note that angular velocity of center of mass of both discs and center of anyone disc about z axis is same, you can verify that if you want, me after verifying it will use it to decrease the length of the...
  44. G

    Vectors - Aircraft's velocity relative to ground

    I attach my working below - my angle is correct according to mark scheme but magnitude isn't (should be 230). I think it's odd that my resultant velocity on a windy day is larger than velocity in still air, but apparently my angle is correct? I've been told that I've calculated the airspeed it...
  45. ILoveParticlePhysics

    Why do things with wheels get more balanced as velocity increases?

    You can try this at home!
  46. P

    Lagrangian mechanics - rotating rod

    Hello, It might sound silly, but when I try to calculate the kinetic energy of a rotating rod to form the Langrangian (and in general), why it has both translational and rotational kinetic energy? Is it because when I consider the moment of Inertia about the centre I need to include the...
  47. nick26

    Measure angular velocity and acceleration from missing tooth wheel

    Hi, I need to come up with a math model for a digital ignition system. I've been thinking about it and I think that I need to measure 2 things to be able to calculate when I have to start charging the coil. They are the angular velocity and the acceleration but how can I do it? the idea is to...
  48. A

    Milky Way Velocity: How Fast Does Our Galaxy Move?

    Do we know at which speed the whole milky way is moving around in the universe? Around the next cluster I suppose?
  49. T

    Blower fitted with a velocity stack

    Many of us know about velocity stacks. It's a proven fact that velocity stacks can enhance the performance of internal combustion piston-cylinder engines. I want to know if a velocity stack is added at the upstream (just before) to a blower/fan, whether it can enhance the performance of the...
  50. A

    I Recession Velocity near Cosmological Boundary: Hubble's Law?

    I'm confused whether Hubble's Law applies to objects near the cosmological horizon (CH). I'm told that objects asymptotically approach the CH and freeze there (v -> 0) in the same way that occurs during in-fall towards a black hole. But Hubble's Law says that velocity is proportional to...
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