avg1(55 km/h)( /2) (90 km/h)( / 2)72.5 km/hDTTsTT+===which should be rounded to 73 km/h. (b) Using the fact that time = distance/speed while the speed is constant, we find avg2/255 km/h90 km/h68.3 km/hDDsT=+which should be rounded to 68 km/h. (c) The total distance traveled (2D) must not be confused with the net displacement (zero). We obtain for the two-way trip avg72.5 km/h68.3 km/h270 km/h.Ds+(d) Since the net displacement vanishes, the average velocity for the trip in its entirety is zero.(e) In asking for a sketch, the problem is allowing the student to arbitrarily set the distanceD(the intent is notto make the student go to an Atlas to look it up); the student can just as easily arbitrarily set
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