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University of Ghana

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• A car moves 26 km due east then 14 km due north. It then turns along a path running north-west with 15 km, then 17 km due west. If the time for the entire journey is 2 hrs.
• Find;
• (a) the car’s average speed in m/s
• (b) the car’s average velocity in km/h

  • University of Ghana - ,

    Average speed = (26+14+15+17)/2 km/h
    =36 km/h
    =36x1000/(60x60) m/s
    =10 m/s

  • University of Ghana - ,

    (a) For the average speed, divide the total distance travelled, in ANY direction, by 2 hours. That would result in:
    (26 + 14 + 15 + 17)/2 = 36 km/h = 36000 m/3600 s = 10.0 m/s

    (b) For the average velocity, divide the distance between the starting and finishing points (a vector sum) by 2 hours.
    The vector velocity from start to finish is
    (26i + 14j -10.607i + 10.607j -17i)/2
    = (1.607i -24.607j)/2
    (i represents the east direction and j represents the north direction)
    = 0.803 i -12.304 j

    The magnitude of the average velocity (average speed) is 12.33 km/h, and the direction is slightly north of west.

  • University of Nairobi - ,

    Simple question
    :D

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