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. Physics lover

    Velocity after t seconds with a time varying Force

    Figure given in question-: I first found out the time when force will be equal ro friction.After force becomes equal to friction there will be no acceleartion further,so velocity after that time will be same.I calculated the velocity by getting a relation of it with time.I got the velocity as...
  2. G

    I Hubble's Law and Star Velocity

    Hubble's Law and Star Velocity By using Hubble's law and the principle of velocity superposition of relativity, we can deduce when the distance of star from the observation point is (photometric distance)r, its velocity V can be expressed as: V = Csin (Hr/C) Therefore, the...
  3. C

    I Accelerator Particles: Speed of Light & Mass Increase

    In an accelerator when you're pushing/pulling a charged particle with a field that travels at the speed of light why should we expect to the particle to exceed the speed of light.
  4. andrea1313

    I Maximal parallel velocity

    so I have this problem from olympiad the maximum value of the satellite velocity component parallel to the high axis of the ellipse(a) and the answer should be vmax=a/b*sqrt(G*M/a). How to prove this?
  5. J

    Inclined Plane, Centripetal motion: Find the Velocity that suits the Turn

    So here is what is going on in my mind: We have a turn that is 400m away from the center of the turn. The faster the car goes, the harder it is for it to maintain its radius. We have a component of the normal force that points towards the center, and static friction which does the same. I...
  6. e2m2a

    A The Higgs Field, constant velocity, and the acceleration of particles

    I need some clarification on how the Higgs field work. The popular science explanation explains the effect on moving particles the way an object would be impacted by moving through a medium of maple syrup. I understand this is a very bad, inaccurate analogy. What I want to understand is does...
  7. Shivam

    Find Velocity of the wooden block at t=4 sec

    Here's the given F-t graph My Attempt... Fsmax=10N & Fk= 5N I made equatiom F=5t-5 ( by seeing Force force and Counteracting kinetic friction) reduced the formula to a=(5t-t)/2 wrote a=dv/dt and solved it but got wrong answer.
  8. A

    Maintain a constant velocity for a rotating wheel

    I want to make a small mechanical calculator with no electric parts, nothing too advanced but a few binary gates capable of some basic functions. All the examples I were able to find were amazing but were still dependent on electricity to drive the mechanism. One possibility is a spring but I...
  9. nuuskur

    Effects of velocity on weight (mass?)

    A ballistics-esque question. Suppose we are driving at ##x \text{ m/s}## and we have to suddenly brake. For students in driving schools they are told something along the lines of "during the braking, the body experiences ##y \text{ kg}## of force" or "the mass of the body is much higher than at...
  10. pobro44

    Two body problem, velocities of two bodies, relative velocity given

    When only force acting on body is a central force, angular momentum is constant and given by: L = mr^2 * w where r is distance from origin, and w is angular velocity. Angular momentum can also be written as following: L = r x mv = rmv * sin(theta) where v is tangential velocity, which is...
  11. V

    Mechanical vibrations: maximum velocity

    So I am almost sure I know how to solve this, just curious about the maximum velocity. Anyway, if you could double check my calculations, here it is. ##T = \frac{t}{n} = \frac{10s}{15} = \frac{2}{3}s## ##\omega = \frac{2\pi}{T} = 2\pi \frac{3}{2} = 3\pi## a). position at ##t = 0.8s##...
  12. A

    Finding the velocity of a skier

    Problem Statement: 1.I'm asked to find the northerly and easterly velocity of kite skier. the skier is moving 25 ms^1 in the N 25degrre E direction. 2. Wind from the west makes the skier accelerate to the east at 2.0ms^1 for 1.8s CAlculate the new velocity. 3. Use the answer from (1) to...
  13. K

    MATLAB Spring mass impact system in Matlab - How to correct it?

    I am new to Simulink and I wanted to start practicing using a spring mass damper system. My first tutorial was this: Later, I wanted to model a spring system where a mass moving at a known velocity hits the spring. The governing equation and a similar modeling method given in the previous...
  14. A

    Motion Along a Straight Line: Calculate velocity of a stream

    Not sure how to go about it
  15. N

    Calculating a velocity formula using air resistance

    Yeah, not sure what to do
  16. Amitayas Banerjee

    What is the angle between the velocity of and the normal to the racket?

    My approach: Let us take two orthogonal axes: x, parallel to the racket's plane and y, perpendicular to it. For the ball to not spin, the components of initial velocities of the racket and the ball along x-axis must be same. Also, as the line of collision is along the normal to the racket's...
  17. S

    Find v(x) of a mass suspended from a spring

    Hi all, I have a problem that I've been grappling with for the past 2 hours. I was confident at first that I found the correct solution, but when I tried to verify I didn't have a constant in my v(x) function. Here is my attempt: I appreciate your help kind internet strangers!
  18. R

    I The velocity of a moving frame of reference

    In the attached fig 1 you have a moving frame of reference (MFR) moving in the direction V at velocity V Looking from above in the MFR there are 2 identical train carriages (car 1 and car 2), Car 1 is on a long set of tracks. Car 2 cannot move but is on train tracks. There are also 2 Identical...
  19. S

    Velocity, acceleration, jerk, snap, crackle, pop, stop, drop, roll....

    Edit: I see this was discussed in the related thread sorry for a repost. If acceleration causes a change in velocity, and jerk causes a change in acceleration, snap causes a change in jerk, crackle causes a change in snap, pop causes a change in crackle, stop causes a change in pop, drop causes...
  20. HRubss

    Determining the final velocity and acceleration magnitude traveling along an arc

    Problem Statement: The motorcycle is traveling at 40 m/s when it is at A. If the speed is then decreased at v'=-(0.05s)m/s^2, where s is in meters measured from A, determine its speed and acceleration when it reaches B. I attached a picture of the problem. Relevant Equations: S = S_0 + v_0(t)...
  21. A

    I Coherence length of velocity fields

    I have came across a term "coherence length of velocity field ##\lambda## ",tried to search in the internet but doesn't find any result...will anyone please give a brief summary of this in this context..
  22. D

    Kinematics problem: Determine the velocity of this car during braking

    Step 1. Integrate the function --> it comes out to -1.8t3+t2-8t+c Step 2. Figure out the integration constant --> I know that the velocity of the car is 30m/s at t=0s so making 30m/s = -1.8(0s)3+(0s)2-8(0s)+C it would seem that C is 30m/s Step 3. Calculate velocity at 4s --> V(4s)=...
  23. M

    Calculate the Angular Velocity of an Arm from a Data Set

    Hi, a newbie to the site and hoping someone can help. Its been a long time since I studied physics or math at school. I am having some difficulty calculating the angular velocity of the arm trhough a partial movement (phase). The data set I have separates the angular velocity into the three...
  24. M

    Velocity of COM after collision

    I calculated that the velocity of the head prior to the collision is sqrt(2gh), as all of the gravitational potential energy is converted to kinetic energy. And I believe the velocity at point A after the collision is given by the formula vf=e•sqrt(2gh), with e representing the coefficient of...
  25. K

    Coefficient of friction for constant velocity given a constant force

    ...
  26. J

    Equating two formulas for root-mean-square velocity

    (a) My question : Are all the formulas correct? If so I can write ##v_{rms}## in form (2) and compare that result with the other velocities to get the answer (rms > average > most probable)
  27. T

    Velocity of a slider immediately before impact

    T1 + V1 = T2 + V2 0 + mAgh = 0.5mAV2A1 + 0 40 = (5/32.2)VA2 VA1 = 16.0499 ft/s Edit: Accidentally Used two notations for Kinetic Energy in the "Useful equations" section. Changed it to correctly notate Kinetic and Potential. This notation is used in R.C. Hibbeler Dynamics 14th Ed.
  28. D

    MHB Angular Velocity - 2100 Revs in 3 Mins - 73.3 Rad/s

    (i) A rotating machine shaft turns through 2100 revolutions in 3 minutes. Determine the average angular velocity, w, of the machine shaft in rad/s. the answer for this is 2100 x 2 pie = 4200 pie radian 3 mins = 180 seconds 4200 / 180 = 73.3 rad/s (ii) Determine the area and arc length of the...
  29. J

    Unable to clearly understand relative velocity

    Unable to understand why this is the case? Also, if it were in two dimensions then I am guessing the same would apply, only the 'x-co-ordinates' and 'y-coordinates' would add up separately? Lastly, does the same hold for acceleration. I am aware that this is a trivial question, many books...
  30. R

    Center of Mass of acceleration and velocity

    I don't understand what I am supposed to do. I know how to find the acceleration of the system, but I am not sure how to find the com acceleration. My guess would be something along the lines of xcom = (m1a1*x + m2a2*x)/(m1a1 +m2a2). Then do the same for the y axis. Then to find the velocity all...
  31. E

    Circular Motion Question: Change in Vector Angular Velocity

    Hi i am e-pie's brother and he let me use his account.Since $$\vec{\omega}$$ is always perpendicular to the plane.Shouldn't this be $$0^o$$?
  32. M

    How to find the velocity of a wave in simple harmonic motion given time

    The graph provided is below. The problem asks for the speed of the wave at 0.12s. I used the formula v=w*xmax*cos(wt), provided in our textbook where xmax is the amplitude of 2 cm, w (omega) is 2pi divided by the period of 0.2. However, for some reason this formula doesn't give me the correct...
  33. T

    Sonic velocity inside a convergent nozzle

    This time, i have a question that came to my mind a few days ago. There is an ideal nozzle having inlet to throat ratio of 8:1. Air will enter the nozzle at around 84 m/s velocity. it can be easily understood that the velocity will become sonic much ahead of the throat. And I am wondering what...
  34. H

    MHB Velocity Time graphs: Find acceleration in the first 15 mins in km/h^2

    Helpp meee pleaseee
  35. K

    Hard time with this Vector Velocity Problem

    Summary: I've posted this in a few forums but still confused on this problem. If the plane is moving at 200km/h and the wind pushes the plane with a velocity of 85km/h, then the resultant velocity would be 217km/h, and using sine inverse, 217.sin(theta=85, I got 23°, which is B, but the answer...
  36. O

    Dynamics Problem: Determine Velocity and Acceleration of Rigid body

    Hello, Wanted to know if this was the correct approach to solve this example. I uploaded the question along with an attempt. Thanks in advance.
  37. lilymay992

    What is the maximum speed of a proton if its kinetic energy is 1.28x10^-14 J?

    So first I tried to use KE=1/2 x m x v^2 but then realized I didn’t have the velocity and I can’t figure out a way to obtain it. I then tried to work out the energy using a different equation, W= q x v but that left me with 1.28x10^-14 J which seemed too small. I also then have to calculate the...
  38. pluralangel

    seeking help finding the initial velocity of a type 3 projectile

    hi, so I've been trying to find the initial velocity of this projectile; but i ended up getting a negative value for seconds squared. I've gone over my solution multiple times but don't see where i went wrong. alternatively, was i supposed to take the absolute value of seconds squared? thanks...
  39. rexxii

    Velocity required between two connecting shafts

    Summary: Constant Velocity between two connecting shafts? Many mechanical machines have a requirement for two shafts to be joined. Explain the requirements for constant velocity ratio between the two shafts? I think this is to do with the requirement for continual acceleration and direction...
  40. G

    How does the release angle of a catapult affect the object's velocity?

    [Moderator: repeated text removed.]
  41. N

    How to calculate change of velocity after hitting water?

    Me and a Partner are presenting the physics of diving as our final in physics. He wants a ton of detail about the activity we choose so I thought it would be a good idea to show the difference from a cannonball vs a normal dive and the change in velocity that occurs with both, and also how much...
  42. I

    Where does the equation of the velocity of a free vortex come from?

    I am aware of the equation of the velocity of a forced vortex, which is simply ## v = r\omega ##. However, the velocity for a free vortex is ## v = \frac{c}{r} ## (## c ## is the 'circulation constant', ## r ## is the radius, ## v ## is the velocity and ## \omega ## is the angular velocity). I...
  43. vsarnaud

    4 Linkage system: velocity calculation

    For the attempt at a solution view the Excel screenshots (1). A screenshot with all the lengths is provided (2). The 4-linkage system is shown in screenshot (3). The problem is shown in screenshot (4). A screenshot from the whole assembly is also provided to add some insights (5). Thanks...
  44. olgerm

    The derivative of velocity with respect to a coordinate

    Why ##\frac{\partial (0.5*m*\dot{x}^2-m*g*x)}{\partial x}=-mg##? why ##\frac{\partial \dot{x}}{\partial x}=0##? Why ##\frac{\partial (0.5*m*\dot{x}^2-m*g*x)}{\partial \dot{x}}=m*\dot{x}## ? why ##\frac{\partial x}{\partial \dot{x}}=0##? Does it assume that speed is same at every location? I...
  45. S

    Find the velocity of the ball

    Hi all! I was attempting the following question but my answer differed from the given answer. Please help me to solve it. Thanks. My answer = 2.45 m/s Given answer = 3 m/s
  46. James Beedy

    Recessional Velocity of a galaxy

    I need to calculate the recessional velocity of a galaxy 500 Mpc away. I need to express my answer in KM, distance in speed, age of the universe in seconds and years.
  47. emarie

    Calculate the magnitude of the velocity at point from a given equation, a(t)

    These questions keep appearing in my past-papers and yet at no point in the course notes can I find a worked solution. Unfortunately I'm not sure where to start. My initial thoughts were regarding getting an equation using known values but w.r.t. to t and integrating for v, but like I said I...
  48. D

    How to find the velocity of a water leak in a spinning tank

    We have a cylindrical water tank that spins over its axis of symmetry with constant angular velocity ω. Here's a diagram: We wish to find: 1 - The tangential and radial components of the velocity of the water as it leaves the tank. 2 - The radius r reached by the water. I'm not sure at all...
  49. P

    Finding the change in velocity through a potential difference

    We're given the equation qB=mv/r which is simple enough. I just don't know how to find the velocity given the acceleration through a potential difference. I tried using the radial acceleration equation given to me but I end up with the square root of a negative...and that breaks math... I...
  50. T

    Relative Velocity of Swimmer: How to Calculate Total Time for Different Paths?

    So I was just wondering if someone could check my method for (b) as sometimes I can have a tendency of getting the relative components wrong ect. Diagram 1 (a) Time for PY: ##T=L/c## Time for YP: ##T=L/c## Total Time:##2L/c## (b) Velocity for PY: ##c-v##...
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