F.4 Maths Question

After the braske has been applied,the distance taken by a car travelling at vkm/h to stop completely is given by (0.006v^2+0.2v)m.How fast was the car going before the application of the brake if the distance taken for it to become to a complete stop was 11.4m.

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  • wkho28
    Lv 7
    10 年 前
    最佳解答

    After the brake has been applied, the distance taken by a car travelling at v km/h to stop completely is given by (0.006v^2+0.2v)m. How fast was the car going before the application of the brake if the distance taken for it to become to a complete stop was 11.4m.

    The distance taken is : 0.006v^2+0.2v=11.4

    0.006v^2+0.2v-11.4=0

    (0.006v^2+0.2v-11.4)X500=0

    3v^2+100v-5700=0

    (v-30)(3v+190)=0

    v-30=0 or 3v+190=0

    v=30 or v=-190/3 (rejected, v is positive)

    The car was going at a speed of 30 km/h.

    資料來源: wkho28
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