1969-02-05 — Page 23

育教僑華頁三第張六第 B%+A=TERRE WAH KIU YAT PO

報日僑茶

三期星日五月二年九六九一愍公年八十五國民華中

(接第六張第二頁)

1969

物理科

(十四)

陸永燁

PHYSICS:(14)

25.50lution

If a given mass of gas at constant pressure za slowly cooled, its volums decreases uniformly with the temperature as shown by the straight lino AB. As the gas is cooled below 0°C. its

volume shrinks further and, theoretically, unere is a definite temperature at which the volume of the gas would become zero. This temperature 18. known as the absolute zero. When temperature are measured from the absolute zero they are said to be absolute temperatures, and are expressed in. "degrees Kelwin" (°K),

The absolute temperaturs TK corresponding to a temperature in Centigrade t°C is given by

1273 t

(b) Suppose the absolute temperature x°C below 0°C. Then, assuming the change in volume takes place at constant pressure, the volume is proportional to the absolute temperature. Hence

constant

1.035

The absolute zero so calculated is

270.790

20-cm. capillary tube 15 heated to get. rid of all traces of moisture and sealed in a flame at one end. A pellet of mercury about 2 cm. Long is introduced at the open and by heating and cooling. The tube is then tied to a clamped ruler together with a thermometer. The combination is put into a beaker of water which is heated by a bunsen burner. A constant stirring is made. The volume of the trapped air. and its temperature are taken. A graph of volume ágainst temperature is slotted showing that the volume of air increasea uniformly with temperatura

With open end upwards, Pressure of air trappsa (8 ~ 5) cm. of he Volume of air trapped

P1VI (H5) 22.4

with open end downwards, Fressure of air trapped

Yolume of air trapped -

212 ~ (H - 5) 25.6

22.4

(H5).

cm of g 25.6 cm. Long

Whère H ia the barometric Applying boyle's law

(115)22.5 CH-

32H 240

H=75

Ans. The atmospheric pressure 13.

merc

(0)

The pressure or air enclosed by the marcury pellet remains constant when. the temperature is raised, being equal to atmospheric pressure plus

cm. of mercury.

Therefore, applying Charles Jaw, and, suppose the pellet rises h ca

30..5

30.5 h

30.5

373

278

英文科

(十四) 劉士俊

Another "tax is paid on goods such as

A jewellery, new clothes, tobacco, vine,

when they are brought into a country. Such

tax is paid as part of the price of these goods

if they are later sold in shops. We call it

indirect tax, because it is paid indirectly through the shopkeeper.

Feople usually complain about having to pay taxes, but they forget that the money is spent on things that they and their families need. We need policemen to catch thieves. to see that

men obey the laws, to direct traffic, etc., and they must be paid what they carn; children need education and there must be schools and teacherni we want our streets to be kept clean, and the wages of men who do thie kind of work have to de paid.. About all, the country must always be ready to defend itself against attacking enemies, and

** we cannot have an army without paying for

Here are ten sentences about the story. Some of them are true and some are not. Put a tick against the ones that are true.

(a) The government decas money to pay for many

things();

b) The money the government needs can be supplied

by the people of the country..

(c) People should not pay money to the government,

(d) The government has a lot of money paid by

the people of other country.

(e) Tax paid according to a person's income 10

called a direct tax.

1)

A doctor should not pay income tax, [)

(1) A tax paid on goods is called direct tax. (1) People should not complain about having to pay

taxes. (a)

(1) The wages of government school teachers are

paid by the government..

If the word in capitais rhymes with one of the following words, write a letter against the number in the space. If you cannot find any word that rhymes with the word in capitale, don't write anything in the space.

Ereapleen

BLOOD

WATCH

(a) blew. (b) qua, (c) nad; (d) gön Fa) wash, (b) care. (4) march(d) teach

SIZE (a) these, bliss, (clbest,(d)fest PIGS (a)bees, (b)bags, (c)picks, (d) seeks LATER (a)fatter (thater, (c)letter, (d)bat (4) TOUR (a) boot, (b)boat)tore.(a) poor (5) PRICE (a) five. (b)kates. (c)kiša,(c) is.

Put a tick against the word which best completes the meaning of the passage

A poet once said "God made the

and but

country.

man made the town.

This

since.

20°C

Any change in temperature will affect both the pressure and volume of the introduced air in the tube. So, the gas squation is used:

V1

Assuming che mercury column at 40° to be Hcm, and the cross-sectional area of the tube.

Sq.cm.then:

273-201 293

1273

40 = 313

-76 51017

40 - 36 cm.

R}1cm.

Substituting into the gas equation

36 x 45a (76-H)(85 - Ha

293

313

-16 1H¥**5460*-*1730

#2}=-151H>=4730x=-0

161

16920

Unly the second solution is possible and therefore, the mercury stands at a height of 38.7 cm. at 40oC.

(a) To verify tharles! Lawifor gases

278

30.5

278.

1014

Ans. The pellet will rise iU.4 cm.

Questions for next week:

(a) Derine specific heat,

Name two different units or specific neat. (b) Describe how you would determine the specific

heat of a solid by a method of mixture.

(c) What volumes of iron, lead, and aluminium care: the same thermal capacity as a litre of water? The specific heat of iron, lead, and aluminium are respectively 0.12, 0.031, and 0.22; and their specific gravities, 7.5, 11.4 and 2.7. (d) Two exactly similar copper calorimeters, each

of mass 50 gm. contain 100 c.c. of water and turpentine respectively at a temperature of 90°. They are allowed to cool under identical conditions and is found that the times of cooling from 70° to 60°C are 5 min. 20 sec. water and 2 min. 7 sec. for turpentine, what is the specific heat of turpentine? Density of turpenting-0.87 gm./c.c. Specific heat of copper 0.10

28, (a) What is meant by the latent neat, or vapori

of a substance?

Name two different units of latent heat.

b) Describe how you would determine the latent

heat of vaporization of steam.

(o) Water in a vacuum flask is boiled steadily by passing an electric current through a coil of wire Immersed in the water. When the potential difference across the coil is 5.25 volts and the current through it is 2.58 amp.y 6.85 gm. of water evaporate in 20 min. When the potential difference and the current are maintained at 3.20 volts and 1.57 amp. respectively, 2.38 gm. of water evaporate in 20 min., all the other conditions being the same. Calculate the latent heat of vaporization of water in joules per gi

(d) (i) In melting to water at 8°C., g. or ice

at 0°C. give up 435 calories. Calculate the latent heat of fusion of ice. (ii) What mass of iron at 1790, droppea into.

liquid oxygen at its boiling-point (-183°C.) will cause 2 g. of oxygen to evaporate? (latent heat of oxygen 51 cal./gm.: ep.bt.sor iron(-0.09 cal./gm./°C.)

the country

MOTS most

beautifu

many

than a town and pleasante:

tox at

live in,

and

too

Many people think

also

this

, and go to the country

For the summer holiday

always even

nëver

BO

though they

cannot live there all the yea

around round too whole

Some

have a cottage in a village. Or

though and

go there

whenever they

could #111 can

ring the time, especially

· must

at weekends.

Answers to Test 13.

(a) were, (b) to do, (6) will be, (d) come, (e) had done, (1) fishing, (g) had done, (h) get, (1) came, (3) has lived.

(a) 1.3, 2.4, 3.0, (b) 1.3, 2.B, 3.a, 4.0, (c) 1.9, 2.-0, 3.A, (a) 1,0, 2.E, 3.D, 4.A, S.P. 6.B "Was it a man or a woman?" asked the shop-keeper. "A man, she answered.

"He was a friend of the woman at your table, said, the man,

"You must go back to your nouse very quickly, I will telephone to the police and ask a policeman to mees you there.".

let the traveller stay in his house. (b) he had lost his purse somewhere outside.

by the farmer'e son.

in the bushed..

e)by the farmer's son.

whom

tan, ailing zand