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0768
英文中學會考試題預習專欄
1908
興發習專桶
物理科
(四)
陸永熾,
英文科。
四
Answers to Exercise II
FYSION (4)
Solution
(a) Archimedes' "Principle states that when a bany 1s
wholly or partically immersed in a fluid it
experiences an upthurst equal to the weight of the fluid displaced.
(b) (1) To determine the Sib, or a plece or stena
The stone is weighed in air (1) before 11 is lowered in water, When it is completely immersed a second reading (W2) is made, making sure that the stone does not touch the beaker and no air bubbles clinging to it. The results are recorded 29:-
Wt. of stone in air
W1
wt. of stone in water W2
Apparent Loss in weight of store W]
Wt. of water displaced
... Specific gravity of atone
Weight of stene in air
ght of water digoladad
WL W1-
(ii) To determine 5.6, ef methylated spirit.
The stone is again immersed completely into a beaker of methylated spirit instead of in water. A third reading (W3) indicating its apparent weight in that liquid. Since the same stone is used, the two apparent losses in weight will be the weights of equal volumes of water and mathylated spirit respectively. The results are recorded as
Wt. of stone in spirit = W3
Apparent loss in weight of stone in spirit
W3
=
-
Specific gravity of methylated spirit
P
Apparent Loas in weight of stone in spirit Apparent losses in weight of stone in water
(e) (1) As the ice cube melts, water will not overflon
Reason:
By the Law or flotation, the Ice cuba displaces its own weight of water. As the ice sits, the immersed volume is less. The exact volume will be occupied by the melted ige,
Student may easily be lead to a faulty answer by Saying that "as 100 melts its volume dinin
no water will overflow
Another way to answer the question 18:-
Assuming, wt. of icp - W
Volume immersed ? V
OH
Volume of water obtained when the whole Ice cube maitse va
In floating equilibrium
W. Va.
a density of water. After the ice is melted
W = vd
From (1) and (2)
Va va
Before melting
(z)
RITSP melting
2.
何玉柱,
She said he told them the truth when they urged him. Op:
She said he had told them the truth When they urged him
The Reason why both answers are possibly is that in the former if we think "when" means "at the time", the clause points out a past time, then we must use simple past tense while in the latter, we may say "when" means "after" (it is possible according to the sense of the sentence,), then we may put "urge" in past perfect tense; in comparing "told" and "said", we knew "told" took place first, there- fore we put "told in past perfect alse.
The man told her that he was not alons as she might think he was. There was 9 young man hidden with him. He(the young gan) was listening, he(the young aan) heard what he (the man) had said. young man had a peculiar way of getting at children. He (the man) said he had seen him do(1) it with his own eyes the day before and threatened her that if she did not obey him, he (the young man, would also get(2) her heart out,
The
Please compare the changes with the taple I gave you last week, you will see.the reason for the changes,
Notes: (1) This "do" is an infinitive
(bare infinitive), it is after the verb 'see", so it is without "to". Be sure not to change it into "did", because this 18.nothe verb.
ས
2
(2) "get" is also a bare infint, tive(infinitive without "to" do not. change it
I hope you have remempered to change the persons and time adverbs.
MORE ABOUT CHANGING SPEECH There are two types of indicative sensen ces: statements and questions. We have dis- Gussed statements. Now we shall look at questions.
There are two ways to ask questions:
To ask without question words.. 9,6, Are you interested in English?
To ask with question words like what, who, how many ete,
e.g. Where have you been?
In Type I, a peculiar verb(or you may say auxiliary or helping verb) is always needed and placed before the subieet.
Verbs that can be used to precede the sub- Jests are; (1) Beslere you there yesterday? (2) Do--Did you invite then?
Have Has he found out the truth?
4) Must--Must we band in our homework?
Shall-Shall we come early tomorrow? 7111--4111 he do it for us?
5
(7)ay--May they co with us?
Can--Can children do such neavy wOTE? Ought (to)--Ought we to study on Sun- dava?
ON
期
日二背月一十年女六九一膺公第六十五國街密中
(10) Used to}--Used they to meet once a
year?
(11) Need--Need hergome?
12) Dare--Dare you walk alone in the-dark?
However, Nos. 11, $12, and 13 may be used as
ordinary verbs; in such ease, they may
borrow the auxiliary verb "Do" to help them As all other ordinary verbs (verbs not inel- aded in the above twelve) do,
é
(10) Did they use to meet oncefa year? (11) Does he need to come?
(12) Do you dare to walk alone in the
dark?
lotice that in (11) and (12) when need and lare are used as auxiliary verbs, thira per- son singular present tense takes still the same forms(without "g") and the main verb La in bare infinitive form (infinitive with- out "to") but when they are used as ordinary verbs, they take "s" in third person singular present forus and infinitive with "to",
(10) ત
In Type 2, we only change the positions uf subject and verb, but if the question word itself is the subject.there is no need to change.
S
Where did you go?(Vero comes first, subject follows)
What happened? (No change)
Now, when we change questions in Type 1. to Indirect speech, besides adding introductory words "He asked then", "He wanted to know ato,, we have to add one more relative word "whether" or "if" then alag change the order of subject and verb. The change in tenses 1a just like that in statements.
B. S. Have they prepared this legson?
Ing.-S.
D
Ing, f.
He asked him whether (1f) they bad prepared, that lesson. Inot question mark.)
Did you tell him I wanted i to ‘zee · him?
We wanted to know whether (if) sne had told him he had wanted to see
When we change Type 2 questiona, we only add introductory words and change word order of subject and verb if necessary; it is at necessary to add other relative words. DI S.
Ind. S. D. S.
B
What is your name?
He wanted to know what nas name was, How much money did you pay for this book?
He asked her how much money, she had paid for that book. EXERCISE III:
Change the following questions intoTM indirect speech:
3.
•
Shall we do the exeraise immediately?
Why didn't he tell me where he had found the book?
Which is the road that leads to the railway station?
4. Does he roully want to go?
5. How could you answer him so smartly?
Use "Be able to")
part of the root is the instep?
6ie whe name given to a large build-
ving in which soldiers live?
Can't we make a more careful search here? When did you see her? (Be careful with this when you change the tenge).
10 Will you go to the moon if you may
ote No.6 and No. 7 ask questions about
things which are true almost all the time j it is possible therefore to keep the same tenses.
LRX
hain
spane
ever
If the tube is placed horizontally.
PUEM:8 am, of Hai Voha c.c.
By Boyle's Law again.
(B+8) 12a 12B 8 x 12
volume occupied the ige volume of water
ebtained from the melted loen
(1) The Box weigne the game in those two gases. Reasoni
By the law of flotatam, the weight of tha bird is equal to the upthrust on at. By Newton'a Third Law of Motion, a reaction force which da equal to the upthrust on the bird acts on the box, So it weighs the game as before.
(111) A body appears to be heavier as it 10 pulled. out of water. Reason:
The upthrust diminishes as less wser will displaced by it when pulling out of wa tar
(d) Let x and y de the barca of the ball in 911 and
mercury, respectively, then
· X
-2-10
By law of flotation,
(3)
Nt. of the ball * upthrust due so od1
Upthrust due to garayry 8.9 % 10 (2)
0.9% -13,09
From (1) and (2)
·sərrugated metal box exhausted of air.
CORDARLOLON or aneroid parometer and mercury carometer:
Anoreid barometer contsing no liquid. It is more sempact than mercury barometer; it is portable, can be used in any position.
Mercury barometers are more agaurate, It does. not constate of metallde parts, The inaaduracy que te friction is avoided. However, the density of mercury and the fragile glass ware demerit the instrument from being portable and acnotaa,
any change in atmospheric pressure alters the Icwer mercury level when mercury rises of falla in the tube, This handicaps the instrument in possessing a permanent calibration on the tube unlesa a mercury reservoir equipped with necessary devices are provided as in Fortin's barometer. Aneroid barometer possesses a calibrated dial. A change in pressure Will be magnified by its lever-system and pointer.
Let B be the stm, preasure: in em, of Hg and a the cross- section of the tube in sa, In, By Boyle's Law,
Pressure x volume « constant BV - RIVI
There
PIV
PIV
ahB
hB
(7-12)B
8 x 12
8 x 12
12
13.3.0)
Ans. The atmospheric pressure is 75.6 cm. of Ag, The
Length of air colum when placed horizontally is 13,3 cm..
Questions for next week:
(a) What are the factors governing the pressure &
any point in a liquid?"
(b) Describe a simple experiment to show the
variation of pressure with depth in a liquid, Explain the action of the hydraulic prase. Water is poured into the thinner limb of a communicating tube containing some maroury. The ratio of the diameters of the two limba la & to 1 How much do the levels on the two limba ribe and fall when the water column is 70 cm.4
Ang. 3.7 die, of the ball is in 911 and
13 nepoury.
(a) Hoyiqla. Law etates that the volume of a fixed
mase of ges La inversely proportional to the pressure, provided the temperature remains gonstant.
ketah diagram or an Android Barometer with ssential marte labelled:
P
(B+8)on of
V1 • 14,8a c.ci
128.0.0.
(B+B) * 12a = (8-8) x 128 12 8 - 14.88
2.88 - 8 x 26.8
8 x 2610
76.6
What are the gonditjane for sne equitanrium of three coplanar forges acting at a point?.
b A light string passed horizontally at a faxed
point Q, over a pulley P to a freely hanging known weight W. Explain how you could find the weight of a body by hanging it on the string between P and Q. C
(c) A heavy uniform rod, 13 11, Long gun weigning 10 lb., is suspended from a fixed point by atrings fastened to its ends, their lengths doing 12-in. and 5 in. Find the angle at which the red is inclined to the vertical and the tensiona the strings,
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