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[Phy] phy最後求救!!! mc 幾條 跪拜!!!

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phy最後求救!!! mc 幾條 跪拜!!!

39,41係完全唔明點計
31.d
39.a
41.d
42.b

41.earth左 仲有CURRENT去 RS?

[ 本帖最後由 lamwaikong41 於 2010-4-18 06:30 PM 編輯 ]
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oh it is ken chan's mock too difficult la
唔明正常la

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引用:
原帖由 nelsonthio 於 2010-4-18 06:32 PM 發表
oh it is ken chan's mock too difficult la
唔明正常la
頂 錯左8條牙 正常

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for 42
佢係generator
咁因為佢turn faster, rate of cutting the magnetic field就faster
根據Faraday's Law, 佢induced 既emf會大左
所以A/B

然後因為佢turn faster, 所以voltage轉方向既rate都快左
then finally B

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31. RATE OF CHANGE OF MOMENTUM = (mv-mu) / t =F
-------> Force (unit N)
-------> only Weight ( W=mg) is using unit N

42. 常理諗 : Rotate faster ---> time taken 小左, 條 curve 嘅 frequency 會快左, 你 rotate 得快左 (motion 勁左) emf 個 magnitude 就會升。 INDUCED CURRENT FLEMING"S RIGHT HAND RULE
====> B

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引用:
原帖由 G_G!smileXP 於 2010-4-18 06:39 PM 發表
31. RATE OF CHANGE OF MOMENTUM = (mv-mu) / t =F
-------> Force (unit N)
-------> only Weight ( W=mg) is using unit N

42. 常理諗 : Rotate faster ---> time taken 小左, 條 curve 嘅 freque ...
OK

那另外2條 THX

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31
rate of momentum change
= change in mv over time
i.e. mv/t =ma = F
as it fall under gravity
thus change in momentum = mg = W
(D)

39
Diameter of P=0.25 Diameter of Q
Cross section area of P= 0.25 Cross section are of Q
Resistance of P = 0.25 Resistance of Q
Current flow of P = 0.25 Current flow of Q
fraction of current flow=0.25/(0.25+1)=0.20 (A)

41
Potential difference of 10V is maintained
thus Vs-Vp =10
Q is earthed, thus Vq=0
Equivalent resistance of the circuit=20 ohm
potential difference between P and Q
Vp - Vq = 4/20 * 10 =2
Vp = 2
Vq - Vr = 10/20 *10 =5
Vr = -5
Vr - Vs = 6/20 *10 =3
Vr = -8
(D)

42
double in rotating speed
time needed to complete a rotation is halved

increase in rotating speed
increase in voltage output
(B)
2012 AL
AL Physics + AL Chemistry + AL Biology + AL Pure + CLC + UE

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引用:
原帖由 lamwaikong41 於 2010-4-18 06:33 PM 發表

頂 錯左8條牙 正常
咁既程度既mock
都只係錯8條

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引用:
原帖由 abchh 於 2010-4-18 06:41 PM 發表
31
rate of momentum change
= change in mv over time
i.e. mv/t =ma = F
as it fall under gravity
thus change in momentum = mg = W
(D)

39
Diameter of P=0.25 Diameter of Q
Cross section ar ...
牙  多謝你詳盡解釋

完全明白了

[ 本帖最後由 lamwaikong41 於 2010-4-18 06:53 PM 編輯 ]

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引用:
原帖由 singga 於 2010-4-18 06:41 PM 發表

咁既程度既mock
都只係錯8條
其實唔係真係太難

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