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Homework Help: Help with average speed/instantaneous speed!

  1. Sep 23, 2007 #1
    Help with average speed/instantaneous speed! :(

    1. The problem statement, all variables and given/known data

    1. EDIT: Figured this one out, now I just need to know about the 2nd question about instantaneous speed.
    2. What is its instantaneous speed at t = 20 s?

    2. Relevant equations

    v= change in x/change in t

    3. The attempt at a solution

    I have no idea how to do this. My textbook doesn't really cover this section well, and I'm just starting out in Physics.
    I did v=2/20 and came out with .1, but I think it's wrong.
    Last edited: Sep 23, 2007
  2. jcsd
  3. Sep 23, 2007 #2

    Is it average speed or average velocity.As it is a displacement versus time graph.
  4. Sep 23, 2007 #3
    Average speed. That's where I'm confused. Why would they give me that type of graph?
  5. Sep 23, 2007 #4
    Average speed is the area of the graph divided by the time.
  6. Sep 23, 2007 #5
    Ok, well I figured out the average speed by doing d/t I think. Either way, it told me I was right, so now I just have the instantaneous speed problem that I don't understand. D:
    Last edited: Sep 23, 2007
  7. Sep 23, 2007 #6
    instanteneous speed is defined as the tangent to the curve at that point(time).
  8. Sep 23, 2007 #7
    So I would use the slope formula to find it?
  9. Sep 23, 2007 #8
    Ya. How did u get the area under the curve.
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