Smile 發問於 科學及數學物理學 · 2 月前

Maths problem, how to do?

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2 個解答

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  • SC147
    Lv 6
    2 月前
    最愛解答

    (a) 

    initial vel., u= 90 km h⁻¹ = 90*1000/60*60 ms⁻¹ = 25 ms⁻¹

    final vel., v= 0 distance travelled, s=33.6 m 

    v² - u² = 2as

    0 - 25² = 2a(33.6)

    ∴ a = - 67.2/625 ms⁻²

    ∴ net force on the car 

    = ma = 1800*67.2/625 kgms⁻² = 193.54 kgms⁻² (to 2 dec. pl.)

    (b) If braking distance is halved, 

    ‬v² - u² = 2as 

    0 - 25² = 2a(33.6/2)

    ∴ a = - (67.2/625)*2 ms⁻²

    => acceleration,a is doubled

    => net force on the car, ma is also doubled

    So, net force on the car = 2*193.54 = 387.08 kgms⁻² (to 2 dec. pl.)

  • 2 月前

    ...........Induction device

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