1)The variable y varies inversely as spuare root x.
If y increase by 20%, find the % change in x.
2)The resistance (R units) of a metal wire varies inversely as the square of the diameter (d m) of the metal wire and directly as its length (l m). If the length of a metal wire 10m and its diameter is 4mm, then its resistance is 75 units.
i) Express R in terms of d and l.
THANKS!
f.4 maths variations
2009-03-01 8:38 am
回答 (3)
2009-03-03 8:06 am
✔ 最佳答案
1. y = k/√(x), where k is a constanty^2 = k^2/x
x = k^2/y^2
y increases by 20%:
new x = k^2/(1.2y)^2
new x = (1/1.44)(k^2/y^2)
new x = (1/1.44)x
percent change = [(1/1.44)x-x]/x*100%
= (0.6944-1)*100%
= -30.56%
2. R = kl/d^2, where k is a constant
75 = k(10)/(0.004)^2
k = 75*(0.004)^2/10 = 0.00012 [or = 3/25000]
So, R = (0.00012)l/d^2
2009-03-02 6:55 am
感謝你的回答
不過翻查答案發現好像有點不同
1) -30.56%
2) R=3l /25 000d^2
不過翻查答案發現好像有點不同
1) -30.56%
2) R=3l /25 000d^2
2009-03-01 9:51 am
The answer is as follows:
圖片參考：http://i320.photobucket.com/albums/nn347/old-master/090301_2.jpg?t=1235843394
圖片參考：http://i320.photobucket.com/albums/nn347/old-master/090301_2.jpg?t=1235843394
收錄日期: 2021-04-29 18:17:28
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