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A certain cable car in San Francisco can stop in 10 s when traveling at maximum speed.?

A certain cable car in San Francisco can stop in 10 s when traveling at maximum speed. On one occasion when the cable car is traveling at maximum speed, the driver sees a dog a distance d meters in front of the car and slams on the brakes instantly. The car decelerates constantly and reaches the dog 8.0 s later, and the dog jumps off the track just in time. If the car travels 4.0 m beyond the position of the dog before coming to a stop, how far was the car from the dog? (Hint: You will need three equations)

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  • 1 decade ago
    Favorite Answer

    Let the initial maximum velocity of the car is u m/s,

    =>By v = u - at

    =>0 = u - a x 10

    =>u = 10a ---------(i)

    The car comes to the halt after (d+4) meter distance and take 8 sec to travel d meter,

    =>By s = ut - 1/2at^2

    =>d = 10a x 8 - 1/2 x a x (8)^2

    =>d = 80a - 32a

    =>d = 48a -----------(iii)

    By v^2 = u^2 - 2as

    =>0 = (10a)^2 - 2 x a x (d+4)

    =>100a^2 = 2ad + 8a

    =>100a^2 = 2a x 48a + 8a

    =>4a^2 - 8a = 0

    =>4a(a -2) = 0

    =>a = 0 or 2 m/s^2

    =>as a ≠ 0

    =>a = 2 m/s^2

    By putting this value in (ii) :-

    =>d = 48 x 2 = 96 m

  • Anonymous
    6 years ago

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    A certain cable car in San Francisco can stop in 10 s when traveling at maximum speed.?

    A certain cable car in San Francisco can stop in 10 s when traveling at maximum speed. On one occasion when the cable car is traveling at maximum speed, the driver sees a dog a distance d meters in front of the car and slams on the brakes instantly. The car decelerates constantly and reaches the...

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  • Anonymous
    5 years ago

    t2 = 10 - 7.44 = 2.56 sec to stop car after passing dog a = 2x/t2² = 2*3.67/2.56² = -1.12 m/s² D = ½a*10² = 56 m (total distance traveled) d = D - 3.67 = 52.33 m

  • Anonymous
    5 years ago

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    Let the initial velocity of the car is u m/s =>By v = u - at =>0 = u - 10a =>u = 10a ---------------(i) By s = ut - 1/2at^2 =>d = 10a x 7.44 - 1/2 x a x (7.44)^2 =>d = 46.72a ------------(ii) By v^2 = u^2 - 2as =>0 = (10a)^2 - 2 x a x (46.72a + 3.67) =>100a^2 - 93.44a^2 - 7.34a = 0 =>a(6.56a - 7.34) = 0 =>a = 1.12 m/s^2 Thus d = 46.72 x 1.12 = 52.28 m

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