physics

the minimum distance that required to stop a car moving at 35.0 mi/h is 40 ft.
(a) express this speed and distance in km/h.
(b) what is the minimum stoping distance of a car moving at 70 mi/h,assuming the same rate of acceleration?express your answer in km.

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  1. a. Vo = 35mi/h * 1.6km/mi = 56 km/h.

    b. V = 35mi/h * 5280ft/mi * 1h/3600s = 51.3 ft/s.
    V^2 = Vo^2 + 2a*d = 0.
    51.3^2 + 2a*40 = 0,
    a = -33 ft/s^2.

    Vo = 70/35 * 51.3ft/s = 102.6 ft/s.
    V^2 = Vo^2 + 2a*d = 0.
    (102.6)^2 + (-66)d = 0,
    d = 160 ft. = 48.3 m. = Stopping distance.

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