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Need Avg. Velocity Equation

  1. Oct 3, 2007 #1
    1. The problem statement, all variables and given/known data

    You ride your bike for 1.5h @ avg velocity of 10km/h, then for 30min @ 15km/h
    What is you average velocity?

    So I think that the variables are this

    Vf=15km/h(.000004m/s)
    Vi=10km/h(.000003m/s)
    Tf=90m(5400s)
    Tf=30m(1800s)

    2. Relevant equations

    That's what I'm asking -_-

    I think that it is
    Code (Text):
    V[sub]avg[/sub] = d[sub]f[/sub] - d[sub]i[/sub]
           ------
           t[sub]f[/sub] - t[sub]i[/sub]
     
    3. The attempt at a solution

    everything I try I get gross decimal numbers -_- Isn't there an easier way???
     
    Last edited: Oct 3, 2007
  2. jcsd
  3. Oct 3, 2007 #2

    Dick

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    Science Advisor
    Homework Helper

    0.000004m/sec is nothing like 15km/hr. I hope you are not using that. Just work in km and hr. You got the right equation though. How far did you travel in all and how long did it take you in all? The quotient is the average velocity.
     
  4. Oct 3, 2007 #3
    so to get the total distance I'd have to do

    d = t/v

    1.5h/10kmh = 15km
    .5h/15kmh = 7.5km
    overall d = 22.5km
    overall t = 2h

    so my average velocity is
    Code (Text):

    v = d/t
    v = 22.5km/h
        --------
           2h
    v = 11.25km/h
    ^ that???
     
    Last edited: Oct 3, 2007
  5. Oct 3, 2007 #4

    Dick

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    Science Advisor
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    ^ That!!! But I've never seen anyone write / for multiplication before. Don't you mean like 1.5hr*10km/hr=15km?
     
  6. Oct 3, 2007 #5
    yeah my bad -_- I hadn't realized it til afterwards; I have no idea what I was typing ^_^

    Thank you so much man!
     
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