You have been called to testify as an expert witness in a trial involving a head-on collision. Car A weighs 690.0 kg and was traveling eastw

Question

You have been called to testify as an expert witness in a trial involving a head-on collision. Car A weighs 690.0 kg and was traveling eastward. Car B weighs 520.0 kg and was traveling westward at 74.0 km/h. The cars locked bumpers and slid eastward with their wheels locked for 6.00 m before stopping. You have measured the coefficient of kinetic friction between the tires and the pavement to be 0.750. 1) How fast (in kilometer per hour) was car A traveling just before the collision

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Diễm Kiều 6 months 2021-07-12T11:58:42+00:00 1 Answers 6 views 0

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    2021-07-12T12:00:28+00:00

    Answer:

    The speed of car A before collision is 3.5 km/h.

    Explanation:

    Mass of car A = 690 kg eastwards

    Mass of car B = 520 kg at 74 km/h west wards

    Distance, s = 6 m

    coefficient of friction = 0.75

    Let the speed after collision is v.

    Use third equation of motion

    v^2 = u^2 + 2 as \\\\0 =v^2- 2 \times 0.75\times9.8\times 6\\\\v = 9.4 m/s = 33.84 km/h

    Let the initial speed of car A is v’.

    Use conservation of momentum

    690 x v’ – 520 x 74 = (690 + 520) x 33.8

    690 v’ + 38480 = 40898

    v’ = 3.5 km/h

     

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