What is Instantaneous velocity: Definition and 114 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. G

    Is acceleration correlated with an instantaneous velocity?

    Is acceleration correlated with an instantaneous velocity? tia
  2. J

    Instantaneous Velocity statement

    Homework Statement "If instantaneous velocity = 0, it is possible to have a non-zero acceleration." Why is this true? I'm having a hard time understanding this. Homework Equations The Attempt at a Solution
  3. X

    Finding instantaneous velocity

    A velocity time graph starts from 0-5 s , object A has constant velocity of 4 m/s. Object B has an initial velocity of 8 m/s and constantly decreases and reaches 0 m/s at 5 s. so i need to know what is the instantaneous velocity. Also, which of the object's instantaneous velocity is greater...
  4. S

    Finding the instantaneous velocity on a position time graph

    I need help with a very general question. I was asked to find the instantaneous velocity of a position time graph at .5 seconds. i know to do this i need to create a line that is the tangent to that point. Here lie the problem... how on Earth do i make that line, and how do i measure the slope...
  5. M

    Explain instantaneous velocity

    The question was, Explain instantaneous velocity. My answer: Limit as delta(t) approaches zero of average velocity is inst. velocity. Or as delta(t) approaches zero, average velocity approaches inst. velocity. inst. velocity is the slope of the tangent line at a given point... Then I...
  6. A

    Instantaneous Velocity with Position v. Time graph

    Homework Statement The position v. time graph for a certain object moving along the x-axis is shown. I don't have the graph. Bu I have the points. (0,-2), (1,9), (4,4), (6,4), (8,-4), (9,0) The object's initial position is -2m. Find the instantaneous velocity at ... (m/s) a.) 0.5s...
  7. D

    Instantaneous velocity in a graph

    Homework Statement http://homework.sdmesa.edu/cmona/195/MP195AFiles/1%20linear%20kinematics%20lab.pdf That is the link to my lab. My question is on page 5: Plot instantaneous velocity as a function of time. Recall that your data only indicates the average velocity of the glider for each...
  8. I

    Direction when the magnitude of the instantaneous velocity is 0

    Hi guys, sorry to ask such a basic question, but I'm studying for the MCAT and need to get my fundamentals down! Anyway, my question is this: Consider an object which has been thrown straight up into the air. It will rise, then at the very top of its ascent, it changes direction and comes...
  9. Saitama

    Instantaneous velocity question?

    Homework Statement The problem is that i am having a doubt in a statement given in the pdf below:- http://ncertbooks.prashanthellina.com/class_11.Physics.PhysicsPartI/ch-3.pdf On page number 6, a line is written "For the graph shown in Fig. 3.6, x=0.08 t3." I am not able understand how this...
  10. C

    How can you determine instantaneous velocity from a position-time graph?

    How would you find the instantaneous velocity if only given a position-time graph?
  11. Femme_physics

    Finding Instantaneous Velocity: Taking the Derivative?

    Taking the derivative seems to be the easiest way of dealing with solving for instantaneous velocity. Should I ever bother with taking the reciprocal, simplifying, or factoring the expression in order to find the 0/0 culprit and cancel it out, or should I just take the derivative each and every...
  12. J

    Instantaneous velocity and acceleration as functions of time

    Homework Statement The position of an object as a function of time is given by x = At^2 + Bt + C A = 8 m/s^2 B = 6 m/s C = 4 m Homework Equations v = u + at a = v/t The Attempt at a Solution I don't even know how to set this up!
  13. I

    Instantaneous Velocity graph problem

    Find the instantaneous velocity at 1 s. Answer in units of m/s. the coordinate for 1s is (1,4) How do i find the instantaneous velocity?
  14. N

    Instantaneous velocity of a object in projectile motion

    Homework Statement stone is thrown horizontally with a initial speed of 8.0 m/s (Vxi) Air resistance is negligible. average acceleration due to gravity = 9.8 N/Kg (down) [ay] Homework Equations dx= Vxi/ time Vfy= vyi + ay x time Instantaneou velocity equation? :S The Attempt at...
  15. L

    How Do You Calculate Instantaneous Acceleration in Physics Problems?

    Homework Statement (X-Axis = Time) 1. Find the instantaneous acceleration at 4 s. Answer in units of m/s2. 2. Find the instantaneous acceleration at 7 s. Answer in units of m/s2.Homework Equations Unknown, I'm assuming you'll use: Acceleration Average = Delta V(final)-V(initial)/Delta TThe...
  16. F

    Instantaneous velocity and cos, sin

    I'd like to apologize for not using the symbols but I spent over 1 1/2 hours trying and after using one of the symbols it wouldn't format correctly for any others. The s^2. s^3 etc... are seconds Homework Statement A particle is moving in one-dimension, and its acceleration in m/s^{2}as...
  17. K

    How Do You Calculate Instantaneous Velocity in Vector Animation?

    Question: A web page designer creates an animation in which a dot on a computer screen has a position of r=[4.0 cm + (2.5 cm/s2)t2)i + [(5.0 cm/s)t]j. a. Find the magnitude and direction of the dot's average velocity between t=0 and t=2.0s. b. Find the magnitude and direction of the...
  18. M

    Instantaneous Velocity Car Problem

    A car is stopped at a traffic light. It then travels along a straight road so that its distance from the light is given by x(t)= bt^2 -ct^3, where b = 2.40m/s^2 and c = 0.120 m/s^3. How do you calculate the average velocity of the car for the time interval t=0 to t=10. I think that maybe I...
  19. A

    Instantaneous velocity- super easy for anyone that knows calculus

    Homework Statement find the instantaneous velocity at 2.00s Homework Equations x=9.75+1.50t3 The Attempt at a Solution I know that lim x/t = dx/dt t-0 So how do I go about solving the differentials.. basically I need a whole course on limits and differentials but i think...
  20. J

    Instantaneous velocity doesn't actually exist?

    can anyone verify my thought process here? so, instantaneous velocity is like average velocity in that it is a slope between two points on a graph of position as a function of time but the two points in a problem with instantaneous velocity are made to be extremely close, almost the same...
  21. J

    Instantaneous velocity electron

    Homework Statement an electron moving along the x-axis has a position given by x=19te^-4t m, where t is in seconds. how far is the electron from the origin when it momentarily stops. Homework Equations velocty=delta x / delta t The Attempt at a Solution i think its a...
  22. M

    Instantaneous Velocity of a car after letting off the throttle

    I have an interesting scenario that a co-worker and I have been arguing over. I noticed that when I accelerate at full throttle to 80km/h then quickly take my foot off the throttle and simutaneously push in the clutch (as to remove the accelerated force) the velocity remains increasing to...
  23. M

    How do I calculate instantaneous velocity?

    Can anyone please explain to me how to work out instantaneous velocity. I do not understand it and how to apply it. Any help would be greatly appriciated. thank you.
  24. C

    Negative acceleration and instantaneous velocity on an object.

    Homework Statement The position of an object along a straight tunnel as a function of time is plotted below: 1. Are there any time intervals in which the object has a negative acceleration? If so, list them and explain how you know. 2. Calculate the instantaneous velocity at t=20s...
  25. H

    Finding Instantaneous Velocity

    The position versus time for a certain object moving along the x-axis is shown. The object’s initial position is −2 m. Find the instantaneous velocity at 1s. http://img23.imageshack.us/img23/5285/phy1w.jpg Using points (0,-2) and (2,7) I found the equation of the line to be =7/2x-2. Since...
  26. N

    Confused on next step in finding instantaneous velocity

    Homework Statement In a time of t seconds, a particle moves a distance of s meters from its starting point, where s=3t^2+13. Find the average velocity between t=1 and t=1+h if (i) h=0.1 (ii) h=0.01 (iii) h=0.001 Use the obtained answers to estimate the instantaneous velocity of the...
  27. F

    Finding the instantaneous velocity

    Homework Statement The questions refer to the attached graph Q1 - calculate the instantaneous velocity of the object at time 2.5s Q2 - calculate the instantaneous velocity of the object at time 7.5s Q3- calculate the average velocity over the time of 7.5s Q4- Is the motion of the...
  28. C

    Determining instantaneous velocity and average velocity using a graph.

    The position of a rabbit along a straight tunnel as a function of time is plotted in Fig. 2-26. Here's the figure: http://www.webassign.net/giancoli5/2_26.gif Determine its instantaneous velocity at the following times. (a) t = 5.0 s (b) t = 30.0 s Determine its average velocity between the...
  29. A

    Instantaneous Velocity at t=4: Solving Displacement Equation s= t^2- 5t + 15

    Q: Displacement in a straight line is s= t^2- 5t + 15. What's the instantaneous velocity when t= 4? Equation: lim [f(a+h)-f(a)]/h as h approaches 0 I tried this problem and what I came up with for an idea of how to solve this makes absolutely no sense.
  30. A

    Anyone distinguish average velocity and instantaneous velocity please ?

    Anyone distinguish "average velocity" and "instantaneous velocity" please ? I can not distinguish clearly between "average rate and "instantaneous rate".Would you please help me and give examples would be glad.
  31. N

    Finding X components for instantaneous velocity with points on a graph

    A test car travels in a straight line along the axis. The graph in the figure shows the car's position as a function of time. (attached figure) Find the x component of instantaneous velocity at points A-G. Could someone please tell me how I'm supposed to go about this problem? I know C...
  32. P

    Jet Engine Displacement, Avg. Velocity & Instantaneous Velocity Calculation

    Instantaneous Velocity?? (stupid question i bet...) Homework Statement A jet engine moves along an experimental track. Its psoition as a function of time is given by the equation x=At^2+B. A=2.10 m/s^2 and B=2.80 m. A)Determine the displacement of the engine during the time interval from...
  33. S

    The instantaneous velocity of a freely falling object

    What is the instantaneous velocity of a freely falling object 10 s after it is released from a position of rest? What is its average velocity during this 10 s interval? How far will it fall during this time? I had asked a few friends for help and I keep getting mixed answers. v = gt 98m/s...
  34. A

    Instantaneous Velocity of a particle

    Homework Statement The position of a particle as a function of time is given by x = ( -2.00 m/s)t + ( 3.00 m/s^3)t^3. (a) Plot x versus t for time from t = 0 to t = 1.00 s. (b) Find the average velocity of the particle from t = 0.150s. to t = 0.250s. (c) find the average velocity from t =...
  35. 3

    Determining instantaneous velocity from a graph

    Homework Statement This is how my problem has been presented: The position of a rabbit along a straight tunnel as a function of time is plotted in Fig. 2-26. http://img134.imageshack.us/img134/8263/graphxt5.th.jpg http://g.imageshack.us/thpix.php Determine its instantaneous velocity at...
  36. F

    Calculting the slope of the tangent to find Instantaneous velocity

    EDIT: Ugh... I meant "calculating", of course. This is an assignment that was due on the 16th. It's already been handed in, I just need some help with a question that I obviously was not able to answer in due time. I am coming back from a long, long hiatus from my academic pursuits and so some...
  37. B

    Instantaneous velocity problem

    Homework Statement find the instantaneous velocity of the particle described in figure 1.1 at the following time a.) t=3.0 s. Homework Equations instantaneous velocity equals dx/dt in the graph, 3 seconds of time is equal to 8 meters. The Attempt at a Solution so would the...
  38. A

    Instantaneous velocity and speed problem

    Homework Statement the position function x(t) of a particle moving along an x-axis is x=4.0-6.0t^2, with x meters and t in seconds. (a) at what time and (b) where does the particle (momentarily)stop? x=4.0-6.0t^2 i made x=0 and i made the equation equal this t=sqrt(4.0/6 =...
  39. H

    Displacement, instantaneous velocity

    If the derivative of displacement is velocity, then what does the integral of displacement (change in position) tell, is it distance? Also what exactly is jerk (third derivative of displacement) and what experiments can you do to measure jerk? How do you calculate the instantaneous velocity of...
  40. K

    Instantaneous velocity of point on a trochoid

    Hi I Googled http://mathworld.wolfram.com/Trochoid.html" but wasn't able to find formulas for the instantaneous velocity of a point on trochoid curves. Does anyone know of an online reference (or know how to find the velocity) I can get rough estimates by calculating the distance between...
  41. S

    Finding instantaneous velocity of objects in projectile motion

    Homework Statement No air resitance Initial speed 8 m/s inst. time at 3 s Find instantaneous velocity at 3s. Components of displacement: dx= 24 dy= 44 Homework Equations d=v1t+(1/2)a(t)^2 or other kinematics equations The Attempt at a Solution I tried to find the...
  42. C

    Average Velocity vs. Instantaneous Velocity

    The graph below shows a plot of velocity vs. time for an object undergoing uniformly accelerated motion. The object has instantaneous velocity v1 at time t1 and instantaneous velocity v2 at time t2. Use the graph and the fact that, when the acceleration is constant, the average velocity can be...
  43. D

    Average and Instantaneous Velocity

    Homework Statement a. Show that if the position x of a moving point is given by a quadradic function of t,x = At^2 + Bt + C, then the average velocity over any time iunterval [t1,t2] is equal to the instantaneous velocity at the midpoint of the time interval. b. What is the geometric...
  44. S

    Instantaneous velocity and time

    can the instantaneous velocity of an object at an instant of time ever be greater in magnitude than the average velocity over a time interval containing the instant?can it ever be less?
  45. F

    Instantaneous velocity problem

    Describe the motion of an object that is initially traveling with a constant velocity and then receives an acceleration of constant magnitude a) in a direction parallel to the initial velocity, b) in a direction perpendicular to the initial velocity, and c) that is always perpendicular to the...
  46. H

    Calculate the instantaneous velocity

    Homework Statement A workman drops a wrench over the side of a high-rise building. Someone looking out their window sees the wrench appear at 11:00 a.m. Another person in an office 25.0 m below the first observer sees the wrench appear exactly 1.00 second after 11:00 AM. Calculate the...
  47. E

    Finding instantaneous velocity at given points on nonlinear graph

    Homework Statement Problem is presented as a nonlinear graph. Y-axis is in meters and ranges from 0.0 to 40.0m in increments of 10m, and the X-axis is in seconds, 0.0-5.0s (increments of 1). Points on graph include (0,10), (1,~19), (2, ~23), (3, ~26), (4, ~26), and (5, ~20). Question...
  48. R

    Instantaneous Velocity methods

    Hello everyone, my teacher taught me there are two methods of finding instantaneous velocity but I didn't understand her. One method was tangents and the other was average velocity at half-time. Could you please explain these methods to me? (in terms of graphical use)
  49. F

    How Is Instantaneous Velocity Calculated in Particle Motion?

    A particle moves in a line so its position at any time in t ≥0 is given by the function s(t)=t²-6t+5, where s is measured in meres and t is measured in seconds. a) find the displacement during the first 6 seconds. All i did was input 0 into the equation solve, then do the same with 6 and...
  50. I

    Instantaneous velocity formula

    I was just confused on what formula i use to find instantaneous velocity if anyone can give me an example or explain how i figure it out that would be great. thanks!
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