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Homework Help: What is the Velocity

  1. Nov 14, 2008 #1
    1. The problem statement, all variables and given/known data
    Tell me precisely what the velocity is when the time t = 5 seconds. include the appropriate units in your answer

    the picture of the problem is here click the link then zoom in to see the actual queston
    http://img372.imageshack.us/img372/7473/43121337ma9.th.jpg [Broken][URL [Broken]

    2. Relevant equations

    3. The attempt at a solution

    I tried adding the full distance divded by 5 but the answers wrong, i aslo tried subtracting the distance then divding by the time still wrong

    then i assumed that it was just the distance by it self 200 divded by 5 but thats all wrong
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Nov 14, 2008 #2


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    Velocity is the instantaneous rate of change of distance at a particular time.

    That would be given on you graph by the slope of the line at the time asked.

    Figure the slope at t=5.
  4. Nov 14, 2008 #3
    okay so its 200 then what?

    should i divide 200 by 5 or multiply it by 5 im lost at this point
    Last edited: Nov 14, 2008
  5. Nov 14, 2008 #4


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    What is the slope of the graph at 5?

    Not the value at 5 ... the slope.

    How much does it CHANGE between 4 and 6 ?
  6. Nov 14, 2008 #5
    it changes 200 thats the difference
  7. Nov 14, 2008 #6


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    The final position for your purpose at 6 is what?
    The initial position at 4 is what?

    The rate of change of position is Final Position less Initial Position divided by the time to change position. So figure the time difference and divide the change in position. That is your velocity. That is also the slope of the graph at all points between 4 and 6 and hence that is the velocity at all times between 4 and 6 seconds.
  8. Nov 14, 2008 #7


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    Not exactly. It changes (-200).

    And the time is what? 2 seconds?

    That means that Velocity is -200m/2s = -100 m/s
  9. Nov 14, 2008 #8
    O..okay thanks for the help
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