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Determine your ave. speed and ave. velocity

  1. Jun 22, 2015 #1
    1. The problem statement, all variables and given/known data
    You swim from one end of the pool to the other end along a straight path with a speed of 6m/sec and you swim back to the starting point along the same path with a speed of 5m/sec. The length of the pool is unknown. Determine you ave. speed for the round trip. How much is your ave. velocity?

    2. Relevant equations
    Ave. velocity = Vf + Vo/2

    3. The attempt at a solution
    I know how to find the ave. velocity, but not the ave. speed.
    Ave. velocity = Vf + Vo/2 = 5m/sec + 6m/sec/2 = 11m/sec/2 = 5.5 m/sec ave. velocity
  2. jcsd
  3. Jun 22, 2015 #2
    Velocity is the vector.quantity.So I think you need to calculate net displacement vector then dividing total time.This will give you ave. velocity
    For ave. speed you need to think total travelled distance divided by total time.

    http://hyperphysics.phy-astr.gsu.edu/hbase/vel2.html It may help you
  4. Jun 22, 2015 #3
    But how do I know the distance traveled or the time? It doesn't show these in the problem so how do I find the ave. speed and ave. velocity without those numbers?
  5. Jun 22, 2015 #4
    You dont need any numbers to find ave. velocity.But for ave speed use your formula.
  6. Jun 22, 2015 #5


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    Science Advisor

    You have enough information.
    The 5.5m/s you've calculated is the average speed, not velocity.
    When you return to your starting point, what is your net displacement?
  7. Jun 22, 2015 #6
    I am trying to tell this from the begining
  8. Jun 22, 2015 #7
    Ave Speed = distance traveled/time elapsed = ??? I don't know the distance or the time.
  9. Jun 22, 2015 #8
    The net displacement is 0?
  10. Jun 22, 2015 #9
  11. Jun 22, 2015 #10
    Ave speed=Total Distnace/Total Time.Lets suppose lenght of pool is x so total distance will be 2x.Now time is t=x/v so total time is x/5+x/6.Find the ave speed now
  12. Jun 22, 2015 #11
    and the ave. velocity is the net displacement divided by the time which would be 0 divided by 0 equals 0 ave. velocity?
  13. Jun 22, 2015 #12
  14. Jun 22, 2015 #13


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    Science Advisor

    Time is not zero. It takes time to swim to the end and back. But, yes, displacement is zero so ave. velocity is zero (v = 0/t = 0)
  15. Jun 22, 2015 #14
    I didnt see that ,sorry
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