紅茶 發問時間: 社會與文化語言 · 1 0 年前

亟需物理能人 解決小小問題

2.Crash Barrier. A student proposes a design for an automobile crash barrier in which a 1700-kg sport utility vehicle moving at 20.0 m/s crashes into a spring of negligible mass that slows it to a stop. So that the passengers are not injured, the acceleration of the vehicle as it slows can be no greater than 5.00 g. (a) Find the required spring constant k, and find the distance the spring will compress in slowing the vehicle to a stop. In your calculation, disregard any deformation or crumpling of the vehicle and the friction between the vehicle and the ground. (b) What disadvantages are there to this design?

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    Lv 7
    1 0 年前
    最佳解答

    一個學生提出一個攔阻牆的設計,可以使一部1700 kg的車子以20.0 m/s的速度撞上時,牆裡的一個彈簧(不計質量)能使車子停止而不傷及人員.但減速度不能超過5g. (a)不計彈簧壓縮時變形以及車子變形和與地面的摩擦力,求彈簧的彈力係數, (b) 這個設計的缺點何在?

    (a) 由能量不滅知車子動能=彈力位能,要以5g的減速度停止(g=9.8 m/s2), 彈簧必須被壓縮的距離為 X=(0-20.02)/(2*5g)=-4.08 m, mV2/2=kX2/2, k=m(V/X)2=1700*(20.0/(-4.08))2=40800 N/m

    (b) 要做出有這麼大的彈力係數的彈簧非常不容易.

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