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Homework Help: Instantaneous velocity

  1. Apr 12, 2005 #1

    I was wondering how to solve the instantaneous velocity for this.

    I have 3 points which have 5 cm between point 1 and point 2 and 9 cm between point 2 and point 3 (this is easy, i just need to grasp the concept)

    The question is "What is the instantaneous velocity for point 2?

    How would I figure this out?

    thanks :smile:
  2. jcsd
  3. Apr 12, 2005 #2
    Do you have any times?
  4. Apr 12, 2005 #3
    oh, yes, sorry,

    the time intervals between the points are 1/40th of a second (lets say)

    (sorry, I forgot to post them... I kinda forgot!)
  5. Apr 12, 2005 #4
    Can you give a little background? What kind of motion is going on here, constant acceleration?
  6. Apr 12, 2005 #5
    it would be variable acceleration, because the consecutive distance between 1&2 is 5 and 2&3 9... so lets say that each time, the velocity increases by one.

    Would I just take the velocity of 1-2 (5cm per 1/40th of a second) and 2-3 (9cm per 1/40th of a second) and find the average of them to get the instantaneous?
  7. Apr 12, 2005 #6
    Define acceleration in terms of velocity. Does acceleration have to change for velocity to change?

    I don't know how accurate you need to be, but what I would do is try to figure out the average acceleration. The object is speeding up, so its position function is:

    [tex] x(t) = x_0 + v_0t + 1/2 * at^2 [/tex]

    We travelled x(t) = 14cm in t=0.05sec. Can you find the acceleration? Can you find the velocity at t=0.025 with this?
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