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-   -   How do I find the average speed of a round trip, to I go 80 mph and from I go 20 mph? (https://www.askmehelpdesk.com/showthread.php?t=473111)

  • May 24, 2010, 04:07 PM
    jaredz1012
    How do I find the average speed of a round trip, to I go 80 mph and from I go 20 mph?
    It is an online homework question that I am stumped on! All I know is that I travel to work at 80mph and from I travel 20mph, and it wants my average speed or avgV!
  • May 24, 2010, 04:40 PM
    KISS

    It's going to be (80+20)/2.
  • May 24, 2010, 05:36 PM
    KISS

    To make you understand it better is 80 mph over some distance D (call it trip #1) and 20 mph over a distance on ( trip 2)

    Thus you traveled 2 times over the same distance. Hence the 2.
  • May 25, 2010, 03:40 AM
    ArcSine
    Agreed that 50 is the arithmetic mean of the two velocities. But if the question is looking for the average speed over the round trip, in the sense of , then you'd want to factor in that you spent 4 times as long traveling at 20 mph.

    Suppose the one-way commute was 80 miles. Then it takes 1 hour to get to work, and 4 hours to get home (why the rush to get to the office, yet so reluctant to return home? :)).

    Then you've traveled 160 miles in 5 hours, for an average of...
  • Feb 22, 2012, 12:06 PM
    Ecreip
    Actually... If it's a round trip, then your average velocity would be 0. Velocity is your displacement/time. If you're arriving back at the same point, then your displacement from the final position to the starting position is 0/time. So 0 units/time units.

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