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Lv 6
help 發問於 科學及數學數學 · 7 年 前

急 ! F5 變分計法 7q02

請詳細步驟教我計以下三條 : 第十四條個表唔識睇,請說明點睇. 唔該晒

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  • fooks
    Lv 7
    7 年 前
    最佳解答

    12.

    (a)

    R : resistance

    v : speed

    R ∝ v³

    Then, R = kv³

    where k is constant.

    When v = vo, R = Ro :

    Ro = kvo³

    When v = 2vo :

    R = k(2vo)³

    R = 8kv³

    R = 8Ro

    New resistance : Original resistance

    = 8Ro : Ro

    = 8 : 1

    (b)

    When v = vo(1 + 10%) :

    R = k[vo(1 + 10%)]³

    R = 1.331kvo³

    R = 1.331Ro

    % increase in resistance

    = [(1.331Ro - Ro)/Ro] x 100%

    = 33.1%

    13.

    W ∝ 1/d²

    Then, W = k/d²

    where k is constant.

    When d = (6400 + 4200), W = 22 :

    22 = k/(6400 + 4200)²

    k = 22*(10600)²

    Hence, W = 22*(10600)²/d²

    When d = (6400 + 1500) :

    W = 22*(10600)²/(6400 + 1500)²

    W = 39.6

    When the space shuttle is the nearest to the centre of the Earth,

    the weight of the spaceman = 39.6 kg

    14.

    (a)

    (To read the graph, read x-axis as "N" and y-axis as "E".)

    (For example, a straight line y = x + 1 should read E = N + 1.)

    E is partly constant C and partly varies directly as N.

    Then, E = C + kN

    where C and k are constant.

    When N = 0, E = C

    From the graph : When N = 0, E = 600

    Then C = 600

    (b)

    Slope of the graph

    = (1000 - 600)/(40 - 0)

    = 10

    vertical intercept = 600

    (Slope-intercept form of a st. line : y = mx + c)

    Equation of the graph (slope-intercept form) :

    E = 10N + 600

    E = 600 + 10N

    (c)

    E = 600 + 10N

    When N = 50 :

    E = 600 + 10(50)

    E = 1100

    Amount that each player pays

    = $1100/50

    = $22

    資料來源: fooks
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