You drive your car in a straight line at 15 m/s for 10 kilometers, then at 25 m/s for another 10 kilometers. a. What is your average s

Question

You drive your car in a straight line at 15 m/s for 10 kilometers, then at 25 m/s for another 10 kilometers.
a. What is your average speed?
b. Choose the best explanation from among the following:
1) More time is spent at 15 m/s than at 25 m/s.
2) The average of 15 m/s and 25 m/s is 20 m/s.
3) Less time is spent at 15 m/s than at 25 m/s.

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Khánh Gia 4 years 2021-08-02T08:28:37+00:00 1 Answers 356 views 0

Answers ( )

  1. thanhcong
    0
    2021-08-02T08:30:11+00:00
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    Answer:

    A) Average speed = 18.75 m/s

    B) More time is spent at 15 m/s than at 25 m/s.

    Explanation:

    Let the first distance be d1 and the second distance be d2.

    We are given;

    d1 = 10 km = 10000 m

    d2 = 10 km = 10000 m

    Speed; v1 = 15 m/s

    Speed; v2 = 25 m/s

    Now, the formula for distance is; Distance = speed x time

    Thus:

    d1 = v1 x t1

    t1 = d1/v1 = 10000/15 = 666.67 seconds

    Also,

    d2 = v2 x t2

    t2 = d2/v2 = 10000/25 = 400 seconds

    Average speed = total distance/total time = (10000 + 10000)/(666.67 + 400) = 18.75 m/s

    From earlier, since t1 = 666.67 seconds and t2 = 400 seconds, then;

    More time at 15 m/s than at 25 m/s.

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