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.

View More On Wikipedia.org
Recent contents Top users
  1. Phantoful

    Bead on a string, find y(x) if horizontal velocity is const.

    Homework Statement Homework Equations K = (1/2)mv2 U = mgh W=Fd Integration/Calculus The Attempt at a Solution I'm not sure what I should be doing for this question, if height changes how is it possible that velocity stays the same, according to the conservation of energy (frictionless wire)...
  2. N

    Maximum Velocity for different accelerations

    Homework Statement Force of jet= A(r(t))4/3 A: constant determined by the fighter model in the class being considered and the drag force on the plane r(t): the rate of fuel consumption as a function of time Consider 3 possible situations for r(t): 1. when the rate is constant for the...
  3. N

    Finding velocity with constant, incre., decrea, varying acce

    Homework Statement Force of jet= A(r(t))4/3 A: constant determined by the fighter model in the class being considered and the drag force on the plane r(t): the rate of fuel consumption as a function of time Consider 3 possible situations for r(t): 1. when the rate is constant for the...
  4. T

    Velocity in polar coordinates (again)

    Hey people, this question was already asked here [https://www.physicsforums.com/threads/velocity-in-plane-polar-coordinates.795749/], but I just couldn't understand the answer given, so I was wondering if some of you could help me by explaining it again. I don't really get Equation (or...
  5. Francis Perez

    Find the Initial Velocity and Launch Angle for a Particular Trajectory

    Homework Statement Hello, so I’ve been trying to find some possible way to calculate this: The initial Velocity and angle needed to launch a projectile and reach the coordinates (x,y). The maximum height the ball can reach before it starts to head down to the target value should be y+5m The...
  6. phantom lancer

    Physics Word Problem: Arrow and moving target collision

    Homework Statement Find the 2 unknown variables.[/B]Homework Equations Am I doing this right? Can someone help me find the solution?[/B] The Attempt at a Solution To compute for the velocity of the target/arrow combination immediately after the collision: M_bV_{bi}=M_bV_{bf}+M_wV_{wf}...
  7. K

    Is The Velocity Of This Object Increasing Or Decreasing?

    Homework Statement Hi everyone, 8th grade physics teacher here. We are doing a handout where we have to identify time-velocity graphs with descriptions. Can you help me with this one? https://imgur.com/a/vEIkg A) The velocity is increasing at a uniform rate. B) The velocity is decreasing at...
  8. fresh_42

    B Third Cosmic Velocity: Will Voyagers Leave Solar System?

    The voyager probes have currently a speed of ##38,000\text{ mph }## which is roughly ##17\text{ km/s }##. Now the third cosmic velocity is ##42 \text{ km/s }## which is far more, and Voyager 2 is even slower. So will they actually leave the solar system, or will they simply orbit in quite big...
  9. Monoxdifly

    MHB [ASK] How much velocity is needed for the rock to be able to hit that bird?

    A bird is located at the (50, 8 ) m coordinate. A boy shot a rock at it using a slingshot with the elevation angle 37^{\circ}. How much velocity is needed for the rock to be able to hit that bird? I substituted all known variables (including the gravity acceleration 10m/s^2, with...
  10. Monoxdifly

    MHB [ASK] Determine its velocity and direction after √(3)/2 seconds

    Something was thrown with an elevation angle 60^{\circ}. Determine its velocity and direction after: a. \frac{1}{2}\sqrt3 second b. \sqrt3 second I tried solving the (a) question by substituting the angle to the equation y=v_0\sin\alpha t-\frac{1}{2}gt^2 and got 0 (the book uses 10m/s^2 as the...
  11. P

    Force decreased but velocity continues to increase

    Homework Statement An object is moving to the right in a straight line. The net force acting on the object is also directed to the right, but the magnitude of the force is decreasing with time. What happens to the object? The answer states that the object continues to move to the right with...
  12. Fia Ismi Nur Alfiah

    Mechanical Physics -- Find the velocity and acceleration of the particle from its position

    Homework Statement [/B] The position of a particle as a function of time is given by r(t) = i(1 - e^-kt ) + je^kt where k is a positive constant. Find the velocity and acceleration of the particle. Sketch its trajectory. Homework Equations v (t) = dr/dt a(t) = dv/dt The Attempt at a Solution...
  13. Philip Dhingra

    I Understanding Length Contraction: What is Limit of Vanishing Transport Velocity?

    I'm trying to understand length contraction from wikipedia, and they mention clock synchronization: The observer installs a row of clocks that either are synchronized a) by exchanging light signals according to the Poincaré-Einstein synchronization, or b) by "slow clock transport", that is, one...
  14. R

    Lift and screw impact velocity

    Homework Statement Consider the elevator and screw in Example 2-17. Assume the velocity of the elevator is 16 mls upward when the screw separates from the ceiling. (a) How far does the elevator rise while the screw is falling? How far does the screw fall? . I have only problem second part of...
  15. S

    Torque required to move a wheeled weight

    I have a problem where I have a large mass on wheels that I want to power with an electric motor. My hope is that I can find the torque i need to start and drive the motor and this is what I have so far. Mass = 400t. Initial velocity = 0 Final velocity = 2.5m/s Distance required to travel =...
  16. F

    Solving The Flight of a Ball: Examining Velocity & Time

    Homework Statement A ball is launched at 10 meters per second at an angle of 45 degrees above the horizontal. What was the duration of the ball's flight? What was it's highest point? When? What was the total distance traveled? Assume air resistance is negligible. Upwards and rightwards are...
  17. Richie Smash

    Calculate the velocity of a body with twice the mass to have the same KE

    Homework Statement A body of mass m, moves with a velocity v, and has a certain kinetic energy. What velocity would a body of twice the mass have to move to have the same kinetic energy. Homework Equations K.E=1/2mv2 The Attempt at a Solution I made an equation 2m1/2*v12/2= m2v22/2 from here...
  18. APphysicsSenior

    Calculating tangential acceleration of rotating object

    Homework Statement An ant clings to the outside edge of the tire of an exercise bicycle. When you start pedaling, the an't speed increases from ) to 10 m/s in 2.6 s. The wheel's rotational acceleration is 13 rad/s^s. Determine the average tangential acceleration of the tire. Homework...
  19. Z

    I Perceived vs. Actual Velocity in an Expanding Universe

    According to what I've been taught, the distance-related redshift seen by Edwin Hubble is an artifact of an expanding Universe. That is, as light travels through space, space itself expands, redshifting the light (matter is embedded in space and does not itself expand but is instead carried...
  20. shivakumarvv75

    B Velocity of light and absolute rest

    dear sir, light travels with constant speed of 3 x 10^8 m/s. does that mean light is in absolute motion irrespective of the its source?
  21. F

    I Need to Calculate the Speed of Sound for a Lab

    Homework Statement Calculate the speed of sound in the classroom. You can use: Tuning forks, water, beaker, pvc pipe, ringstands, etc. Homework Equations v = f(wavelength) For fundamental frequency: L = 1/4(wavelength) For fundamental frequency: f = v/4L The Attempt at a Solution Here is...
  22. Skrphys

    Power Equation: Instantaneous vs Average Velocity

    How does this version of the power equation relate to physical situations? Does the value you get give you an instantaneous power? Or is the velocity to be taken as the average velocity (an actual displacement over time)?
  23. D

    Is the Faulty Velocity Equation for Projectile Launch Valid?

    I have seen this equation used to calculate the velocity of a projectile being launched off a table top. Where D=horizontal distance travelled, h=table height, and g=gravitational acceleration. Nowhere else can I find a calculation of velocity based on only two distances and GA. Everything I...
  24. G

    I Basic Q about Vector/tensor definition and velocity

    HI, I have read about tensors and generally understand the concept. One core thing about Vector/Tensor as I understand it is that its magnitude and direction should not change with change in coordinate system. I get that when I write vector and also when I use matrix transformation. However...
  25. I

    Calculating the Velocity of a Catapulted Object

    A catapult is pulled back 10cm with a force of 30N. How fast does the stone of mass 0.5kg got at maximum speed assuming no air resistance. I have absolutely no idea how to do this... But, I am assuming you use Ek=1/2mv^2, though I can't figure out how to apply it To rearrange that...
  26. LonelyElectron

    Deriving an equation for the velocity of a particle

    Homework Statement Derive an equation for the velocity vx(t), vy(t) of the particle. - my teacher writes this oddly, that means the velocity in the x direction at any point in time, and the velocity in the y direction at any point in time. Calculate the initial velocity of the particle...
  27. Sandeep T S

    I Angular Velocity: Can a Body Move Faster Than C?

    When I rotate my head with 1rad/s , I can see a body which 350000km away have velocity greater than c.is that possible?
  28. Kerdo

    Find the object's acceleration

    Hello! Would love a quick explanation of these two exercises :) 1. Homework Statement 1) Find objects acceleration, when mass is 200kg and it is being pulled on a horizontal plane with a force of 2000N. How much work is done on 400m road? 2) An object fell from 200m. How much of its energy...
  29. P

    Water Velocity Question: Impact of Pipe Length on Flow Rate

    For a vertical pipe of water can the pipe length affect the velocity of the water? note: the water is flowing through this vertical pipe.
  30. P

    How can gyroscopes be used to find the angular velocity?

    I was reading that gyroscopes can be used to measure the angular velocity of precession, such as in the Hubble space telescope, but mathematically how can this be done? Many thanks
  31. isukatphysics69

    Rank the vertical component of velocity?

    Homework Statement Rank the vertical component of the initial velocity of each projectile, greatest first.Homework Equations n/a The Attempt at a Solution I took the sine of the angles, the angles are ranked B>A>C>D you can see this visually as well as looking at the maximums. why isn't this...
  32. vcm1992

    Find Initial Velocity Given Height, Range, and Initial Angle

    Homework Statement So! The problem states that a grasshopper jumps from the edge of a table. We know that x-initial is zero and x-final is 1.06m. This is how far he jumped from the origin. The height of the table is unknown, but we know that the height of the grasshoppers jump with respect...
  33. J

    Relative velocity help -- A bird flying in a wind trying to get to its nest

    Homework Statement A bird can fly in still air at 100km/h. The wind blows at 90km/h from W(x degrees)S. The bird wishes to return to its nest which is due E of its present position. In which direction, relative to the air, should it fly?My textbook says that the velocity of the bird relative to...
  34. vAhmed

    Find final velocity in a horizontal projectile motion

    Homework Statement A ball was thrown from a cliff, it reached to the ground after 2.5 seconds. a) Find the height of the cliff. b) Find the horizontal distance the ball reached. Homework Equations Δy = 2⋅g⋅t^2 Vfy = g⋅t √(Vfy)^2+(Vfx)^2 Δx= Vx⋅t The Attempt at a Solution I've found Δy=30.6m...
  35. almosthavoc

    Centripetal forces | finding coeff of friction with only velocity

    Homework Statement I don't remember exactly what the question was because it was on a quiz today. It said something along the lines of "a ladybug is on a turntable and begins to slip at .5 m/s. Find the coefficient of friction. Homework Equations Fc = (mv^2)/r a = v^2/r Ff = uFn I think...
  36. W

    Escape Velocity and Centripetal/Centrifugal Acceleration

    This is just a reality that I have stumbled upon that I'm sure was well-known, but I still found it interesting. I apologize if this is second-nature to physics experts. I was responding to a post on a different thread that claimed you could make a tunnel around the Earth and if you sent a...
  37. dUDEonAfORUM

    Find transverse velocity given an equation of displacement

    Homework Statement A wave pulse on a string is given by D(x) = D[0][/SUB]/(x[2][/SUP]+a[2][/SUP]), where D0 is a constant with units of cm3 and a is a constant with units of meters. a. If the wave moves along the string at a velocity of v in cm/s, what is the transverse velocity of particles...
  38. R

    Centre of mass of binary system calculation

    Homework Statement Given a graph (see below) containing the velocities of two stars with respect to the sun, I am asked to calculate the velocity of the centre of mass of a binary system. I am not given the mass of either star, nor the shape of the orbit nor the velocity of the centre of mass...
  39. lc99

    Torque and Initial Angular Velocity effect on time

    Homework Statement Homework Equations [/B] T = inertia * alpha The Attempt at a Solution I'm not sure how the torque or angular velocity initially affects the time to speed, but it seems like the more angular velocity , then the quicker the engine would stop. I do know that more torque...
  40. D

    A projectile's initial velocity without time?

    Homework Statement A projectile is launched: Horizontally, with an average displacement of 49 cm Vertically, with an average displacement of 28 cm At a 23 degree angle, with average displacement of 126 cm Homework Equations The Attempt at a Solution I am sad to say I don't know how to do it...
  41. hideelo

    A Velocity dependence of operators in Inonu-Wigner contraction

    I'm reading Weinberg's QFT volume 1. At the end of section 2.4 he is deriving the Inonu-Wigner contraction where he reduces the Poincaré group to the Euclidean one by taking the low velocity limit. In analyzing how the operators depend on velocity there are some I understand and some I don't. I...
  42. V

    Use angular momentum to find the velocity (comet orbit)

    Homework Statement A comet orbits the sun. It's position in polar coordinates is given by, $$r(\phi)=\frac{1.8r_0}{1+0.8\cos{\phi}},$$ where ##r_0## is the position at closest approach. Its velocity at this point is given by ##v_0##. Use the concept of angular momentum to find the following...
  43. S

    Basic average acceleration confusion

    Hi there, I'm struggling to distinguish why the following two equations are giving distinct answers, when the question explicitly states either could be used: v=u+at v^2=u^2+ad when v=12 m/s u=0 m/s a (average acceleration)= the unknown variable d=24 m t=4s Theoretically, the two should...
  44. CollinsArg

    Exploring the Relationship between Work and Constant Velocity

    Hi! I've found some excercices and expanation of Work always consider a constant velocity, this is a net Force equal to cero. Like spring or gravity excercices related against a force applied. Does this relation with constant velocity has some usefull explanation why? Should I always assume...
  45. D

    Initial velocity if a performer clears a 30 m tall object

    Homework Statement In 1940, Emanuel Zachinni, one of a family of “human cannonball” performers, set a world record by traveling 53m. If he clears the 20 m tall ferris wheel (which is 25 m away from the cannon) by 10 m, how fast was he going at launch? Homework Equations range 53m...
  46. T

    Trajectory of a Projectile that must clear an obstruction

    I am trying to solve for Vy with given Vx. I know how to do this for the BLUE trajectory line, but I do not know how to solve this if there is an obstruction in the way (like the gray wall). My givens are: X1 X2 Y1 Y2 Vx Gravity Do I need to solve for the blue trajectory then adjust that for...
  47. G

    Angular Velocity Vector; Relationship to Angular Momentum

    I read in several places that if, for example, a point particle exhibits uniform circular motion about the z-axis within an osculating plane not equal to the x,y plane, then the angular velocity still points along the z-axis, even though the angular momentum does not (it precesses about the...
  48. F

    Velocity needed to escape gravitational potential

    I am solving a problem where I need to decide if an asteroids velocity is high enough to escape the planets gravitational pull. The way I did it was use conservation of energy and angular momentum to find an expression for the radial velocity and show that it remains positive as r tends to...
  49. Specter

    Impulse and momentum in two dimensions - Finding velocity

    Homework Statement In a physics lab, 0.30 kg puck A, moving at 5.0 m/s [W], undergoes a collision with a 0.40 kg puck B, which is initially at rest. Puck A moves at 4.2 m/s [W 30 N] . Find the final velocity of puck B. Homework Equations Conservation of momentum Pythagorean theorum The...
  50. N

    Relative velocity of two cars crashing into each other

    So I read these two other threads: https://www.physicsforums.com/threads/relative-speed-of-two-cars.642873/ https://www.physicsforums.com/threads/two-cars-colliding.740948/ And gathered what I already thought was correct, that the relative velocities of two cars of equal mass crashing into...
Back
Top