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Homework Help: Physics homeowork Average Velocity

  1. Sep 15, 2012 #1
    Hello everyone i need help in my physics homework my class is tomorrow and i ve been trying to solve it since 2 days but i don't now how to

    A driver moves 1/3 of the way between two cities with speed of 60 km/hour

    he continuous with speed of 90 km/hour find the average velocity? the car is moving to the right

    please help me
  2. jcsd
  3. Sep 15, 2012 #2
    You should know that distance moves= average velocity x time.
    Find all the equations that relate to above equation.
  4. Sep 15, 2012 #3
    The formula for average velocity is Δs/Δt, i.e. change in displacement over the change in time (or time taken), as I hope you're aware of.

    Now, what you have to do is find an expression for time, using s for displacement and the known speeds. Try it yourself from there and reply if you're having difficulties.

    What you could do, if you want to simplify the question, is to instert a known value for the displacement. Since the only information you've got is the fraction of which he drove at the two speeds, this wouldn't affect the final answer as the displacement cancels out in the calculations.

    EDIT: I was away and did not notice the above poster. My bad.
  5. Sep 15, 2012 #4


    User Avatar

    Staff: Mentor

    Let the distance between the cities = x km.
    and proceed from there .....
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