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kitty asked in 科學及數學數學 · 1 decade ago

20 分** 1 條Form 2 數,, 入黎睇下啦...

1 條Form 2 數...

http://img12.picsplace.to/img.php?file=img12/2/Mat...

答案係...

51.5

唔該講下點解...

最好有埋解釋...

最好果個會係最佳回答...

thx~

PS*

e 個係用畢氏定理計嫁...

3 Answers

Rating
  • 1 decade ago
    Favorite Answer

    take the midpoint between AB as C,

    the point where the pendulum is fixed as O,

    the lowest point of the pendulum as D,

    OD = 20cm

    OC = OD - 5cm

    = 15cm

    consider triangle OAC,

    OC^2 + AC^2 = OA^2

    15^2 + AC^2 = 20^2

    225 + AC^2 = 400

    AC^2 = 175

    AC = 13.2 cm (correct to 3 sig. fig.)

    AB = 2AC

    = 13.2 x 2

    = 26.4 cm (correct to 3 sig. fig.)

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  • 琴生
    Lv 5
    1 decade ago

    http://i179.photobucket.com/albums/w296/14022007/p...

    請參考上圖.

    OC = 20 cm - 5 cm = 15 cm

    OA = 20 cm

    By Pyth.Thm.,

    CA2 = OA2 - OC2 = 202 - 152 = 175

    CA = √175

    AB = 2CA = 2√175 = 10√7

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  • sam
    Lv 5
    1 decade ago

    do you mean horizonic distance between A and B

    if so, your answer is wrong

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