4. Car A is standing at red traffic light. Just as the light turns green car B travelling at a constant velocity of 14 m.s- passes car

Question

4. Car A is standing at red traffic light. Just as the light turns green car B travelling at a constant velocity
of 14 m.s- passes car A, which accelerates uniformly at 2.5 ms-2 to a velocity of 18 m.s-1 and then
travels at a constant velocity.

4.2 How long does it take car A to reach a velocity of 18 m.s-1

4.3 Which car is ahead and by how much, when car A reaches a velocity of 18 m.s-1

4.4 How long does it take for the cars to draw level?
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Yến Oanh 3 years 2021-09-05T03:59:22+00:00 1 Answers 3 views 0

Answers ( )

  1. vankhanh
    0
    2021-09-05T04:01:12+00:00
    Reply

    Answer: t = 7.2 s, B by 36 m, t = 16.2 s from green light.

    Explanation:

    4.2  18 m/s / 2.5 m/s² = 7.2 s

    dB = 14(7.2) = 100.8 m

    dA = ½(2.5)7.2² = 64.8

    Car B is ahead by 100.8 – 64.8 = 36 m

    36 m / (18 – 14 m/s) = 9 s

    t = 9 + 7.2 = 16.2 s

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