phy~從不知怎麼是對的

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1.the motion of a toy car is recorded by a ticket-tape tine with a frequency of　　
100Hz.the distance between the first two successive dots and the final two successive dots is 1cm and 7cm respectively.also,there are 5 dots on the tape.

find the initial velocity,final velocity and hence the acceleration of the toy car.

initial velocity 應該係1/1/100 =100cms^-1
final 應該係 7/1/100 = 700cms^-1

acceleration係 7ms^-1  - 1ms^-1/ time
個time應該係幾多.. 唔識搵個時間.. 果2個velocity既時間係幾多...?


2.如個1舊石頭被氣球條線縛住,,慢慢由地下升上空中
如果向上係positive
姐係石頭上面既tension既magnitude大過weight既magnitude.
咁佢個acceleration係acceleration due to gravity=10ms^-2 ?
咁佢係向上加速定向上減速...?搞唔清楚呢個問題..好似加又好似減- - " thx

pokedigi

30# 囧囧中自有囧囧

potential difference係唔係姐係2點之間voltage既difference呀??

                               
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我想問X同Y之間既potential difference係幾多??
小霞的fans 發表於 16/4/2010 01:47 PM

                               
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正確的講voltage只是potential 的單位
so 問p.d.(potential difference)姐是問2點(wire上)的potential差幾多voltage
答案是以V做單位
如果wire 2點之間冇其他野,而resistance of wire=0的話,p.d.就是0(V=IR,R=0)
(ce是比較少出現potential 呢個字,但到al 就會是咁講)
一般而言,一個circuit中,battery的emf
(emf 姐是battery 2邊的p.d.,ce有時都會出現)
是等於任何一條route中所有across其他物件的p.d.的總和
除非條題目有講 internal resistance (battery 自己的 resistance)
不過應該是al 先會問
呢條題目得一條route,一個物件,所以佢的p.d.就=emf=6V

囧囧中自有囧囧

02 18 同09 第12題一樣-_,-
heat loss to surronding
energy 大左 E=ml
change of mass 不變 l大左
(2) more energy is required to boil to same amount of water
e大左 change of mass不變 l大左
(3) change of mass大左 e不變ge話 l細左
edited
02 20 mm=mass of metal mw
有水係上面 多左一樣野比energy*
之後點自己諗=P

renz

4. 1997/I/4

                               
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A student uses the apparatus shown in Figure 5 to perform an experiment to measure the specific latent heat
of fusion of ice. He uses a joulemeter to measure the energy required to melt a certain amount of ice.
(a) Draw a diagram to show how the apparatus can be set up for the experiment. (3 marks)
(b) The following data are obtained in the experiment :
Initial joulemeter reading = 28 000 J
Final joulemeter reading = 40 400 J
Mass of water collected in the beaker = 0.045 kg.
Calculate the specific latent heat of fusion of ice. (3 marks)
(c) Why should the ice used in the experiment be crushed ? (2 marks)
(d) A teacher comments that the result of this' experiment is not accurate. She points out that a control
experiment is required in order to improve the accuracy of the experiment.
*(i) Describe how the control experiment can be set up and explain its function. (5 marks)
(ii) After setting up the control experiment, the student repeats the above experiment. Would you
expect the specific latent heat of fusion obtained to be higher or lower than that obtained in (b)?
Explain your answer. (2 marks)

同埋mc兩題

18. 2000/II/21

                               
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The above apparatus is used to find the specific latent heat of vaporization of water lv. Which of the following
factors will cause the result obtained to be larger than the true value of lv?
(1) Some energy is lost to the surrounding
(2) Some steam condenses and drips back into the beaker
(3) Some boiling water inside the beaker splashes out of the beaker
A. (1) only B. (3) only C. (1) and (2) only D. (2) and (3) only E. (1),(2) and (3)


20. 2002/II/21

                               
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The result obtained in Q.19 is found to be higher than the true value of the specific heat capacity of the
metal. Which of the following is a probable reason?
A. Some hot water is still adhered to the metal block when the block is transferred to cold water.(19)
B. Some energy is lost to the surroundings when the metal block is transferred to cold water.
C. Some energy is absorbed by the cup.
D. The temperature of the metal block is still higher than 38ºC when the final temperature of the water
in the cup is measured.

sy

30# 囧囧中自有囧囧  

potential difference係唔係姐係2點之間voltage既difference呀??


我想問X同Y既potential difference係幾多??
小霞的fans 發表於 16/4/2010 01:47 PM

                               
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potential difference=voltage

小霞的fans

30# 囧囧中自有囧囧

potential difference係唔係姐係2點之間voltage既difference呀??

                               
登錄/註冊後可看大圖

我想問X同Y之間既potential difference係幾多??

囧囧中自有囧囧

更正囧我抄錯野--呀sir話係glass ,red light快過violet
wavelength of violet<wavelength of red先岩囧rz
i am so sorry

ice

呀sir話係glass ,red light快過violet
但係wavelength of violet大過red唔記得點解lu
囧囧中自有囧囧 發表於 15/4/2010 09:33 PM

                               
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不是frequency ofviolet>frequency ofred
wavelength ofviolet<wavelength ofred嗎

囧囧中自有囧囧

呀sir話係glass ,red light快過violet
但係wavelength of violet細過red

小霞的fans

violet visible light係glass既speed慢d定red visible light慢d架!?
書裡面冇提過但係past paper出過!?
同埋呢..
T+(mg)=ma
g係negative所以係
T-mg=ma咩
點解係T+mg=ma囧

點解係+既.....