1969-02-12 — Page 23

育教僑華 頁三第張六第 日六七月二十年申戊属夏 WACKIY YAT RO

郭日橋茶

三期昂一日二十月二年九六九一暨公年八十五國民中

1969

「文中學會考試題預習

(接第六張第二頁)

物理科 (十五) 陸永熾

Solution

PHYSICS (157

(a) The specific heat of a substance is defined as

the amount of heat required to raise the

temperature of unit mass of it one degree.

hence the unit of specific heat is calories per gram per decree C" or "B.Th. Der lb. ter degree Fu

fh Determination or specific Heat of a Solid

The specific heat of a solid can be found by heating it in a steam charber or a vessel

ter, then quickly transferring it to a vinster containing, water, and measuring

inal temperature of the mixture. Suppose

193 of water M

19 so of the solid m ip.ht. of the solid S Vass of calorimeter -

Sp.ht. of calorimeter

Initial temp, of water

Final temp of water

Initial toro, of hot sold

པ

en, since heat lost by solid neat gained

by water and calorimeter. assuming no heat

Logs to the outside,

pålt2 = *) * (§ * ®

− +) - (M + ©jsje - tj)

In this equation

is the only unknowri quantity, and can hence be evaluated.

le). The thermal capacity of a body is the

quantity of heat required to raise ita temperature by it is therefore equal to the croduct of the mass and the specific heat.

For 1000 cc. (1000 gm.) of water, the

thermal capacity is 1000 cal.

The product of the mass and the specific neet has to be 1000 for each metal. that is

ms - 1000

1000

The volume is given by dividing the mass by the density

1000

Sp.ht. of calorimeter Mass of calorimeter Da

Mss of calorimeter water

Mass of calorimeter + ter steam Initial temp. of water

Final temp. of water t

Geat lost by steam = Heat gained by

- (

and calorimeter

The Latent heat or steam, L, is the only unknown in the equation and, thus, can be easily eva lua ted.

Another method to determine the latent reat of steem dia as in (c) part of this question,

lel The current passing in the wire, 1 = 2.59 200, The potential difference across, the coil,

V = 5.25 volts

heat produced par second. 12.58 x 5725 joules,

This neật 19 expended in avaporating the water and in gaking up the heat losses' to eu This

英文科

十五) 劉士俊

fal. In ancient days a univer......... was thought as

building in which learned men studied

group of men who had come together to discover new facts and ideas

a place of higher education (

A high school ()

Tha university te a DISCE

where only young people come to receive

higher education l

here only learned men studied and taught

others)

There young men and women may go where teachers are taught

(c) Older men and women

are not permitted to go to a univeтALTY. 1

are permitted to go to a university are not permitted to teach in a university

STE not

not willing to go to a university (d) we can en to a university

to study some special subjects

to teach others

to be taught English

to be a dostor 7. ).

In each of the following sentences put a tick (V) against the word which best completes the meaning.

into

zero 13 e serious fire.

a ship.

Bumoat everything,

(b) They reep & watch

st

(c) TH10 18 your 18st day.

..to

Londo

of

They helped to put the

out without

the required volume s are

1000

Ior ro

ALL C

x. 0.12

1000:

For lead v

2830.0

x: 0.033

1000.

1683

5.25

where 13 the

Leut next or vapor ikết 1on th Joules per grao and h is the heat loas ta surrounding.

In the second case, IV becomes juule

20% 60

The rate of Loss of heat from a surface depends on the degree of polish of the surface. its area and its temperature excess of the surrounding, as the two calorimeters are identical as regards surfaca polish and temperature, and as they contain equal volumes of hot Liquid and therefore the i heated area are equal. the rates of loss of heat must be equal.

For the calorimeter containing 100 gm. water: Loss of beat in 320 seo - (50x0.1+100) (70-501

'fate" of "Loss of neat

(5. 100) 10

*120

calories

cali/seo.

For the calorimeter containing.

(100 x 0.87) gm. of turpentine i

Loss of heat in 127 sec. « [50x0,1+675;"

(70-60) calories. (whera S is the Bp.ht of turpentine!

Subtracting: ii) Fron

16:852.49

20 x 6012.58

2290 joules /gram,

The rent heet of vaporization of Water is 2290, Moules/sram

10 12 Heat absorbed by ice in mating to water

5 calories

(where I is the latent heat of Cualún

of ice

Heat absorbed in raising the ice-h to BU = 5 x 8 calories

5458435

2=435/5

87-

Rate of loss of heat a

(5+ 875)10.

127

ca 1/sec.

Since their rates of heat loss are com1.

•

320

15 875)10

127

201ng to Take you withi

e. You will win honour

Our brav

througn

Harcules:

a nandsome young man,

about!

HO

to leave Hong Kong,

He a

act

ܠܵܐ

Hunting year

(1) Mary sang sweetly-

Into

off

the chois

Lo 79

The Latent heat of fusion of ice 79 calvizi

(11) in cranding 18 of liquid oxygen oxygen gas, it requirs S1 cal.

In changing 2 zu. of liquid oxygen Eas, custaty of heat required - 102 cal. let m be the mass of tron at 1790 used evaporate the liquid oxygen

mx 0.09 % (1718) 51 2 x 9 - 51

Underline the correct word in the brackets

(a) Let Hay and (1, ze) do this work, (u) Each of us must try (his, our best. (c) They work (hard, hardly) in school (a) Cone and ait beside (1, me), (e) I am as tall as (be, him).

Mary and (1, me) go to school. Who is singing? It is (ne, him) (n) he is as strong as (her, she). (1) (Whet, ho) is your name? (A) Henry 18 the boy (whom, who) did it. imavera to "That, la e

(a)

long, (b) by, (C) over, (d) 12, (e) beside," for, (g) abcat, (h) against, (1) from, (5)or. (a) secondary, (b) difficulty, (c) saved. (d) wonderful, (e) slowly.

(a), (b), (e), (s), (1), (J-

(1), (2) c, (3), (4) a, (5)

and, more, to, so, even, round, ano, can.

32015 . 875) - 127 x 105

The specific heat of turpentine is 0.42 cal/gm/

The latent heat of vaporization of a substance is defined as the quantity of beat required to change one gram of it from Loud to a vapour at the boiling-point.

The units are calories per 20® #B.Th.U. per lb.

(b) Determination of latent heat of steam

The method of mixture.

Some water is boileo na rask, 800 using "atean trap" steam alone is obtained. Tha steam is then passed into a calorimeter containing water. The final temperature as well as the initial temperature is recorded, The mase of steza condensed is obtained by ramsighing the calorimeter and its contents The difference between this weighing and that before ataam is condensed will register the mass of staan, with the following measuremoŋça, the latent mat of steam is calculated:

Ang. Fron used in. vaporating the

Itould oven is 2

THE STONE for the next week

zy, to cxpis in the term "mechanical equivalent or

eat" Name two units of it.

b) Describe the simplest method you know of

measuring the mechanical equivalent of heat (c) The height of the Niagara Fall is about

150 ft. What is the difference in temperature of 1 lb. of water at the top of the water fall and the same water at the bottom?:

(a) A meteor. mase 10 ka.. has its speed reduced

30

by sir resistance in passing througn t he atmosphere. Calculate the tots) quantity of heat developed as its speed changes from 600 m/s to 100 m/s. (J - 2.19 joules/on 1,1 tal A plane mirror 10 on, long 18 placed 45 cm. In front of the driver of a car, Through what width of rear window, 135 or behind him, can ha 9se when locking into the mirror? (b) raw diagrams to show how it is that a

Convex lens has a wider field of view than a plane mirror of the same size.

(c) Determine the position and size or une image of an object 1 in. high, placed at distances. of 6 and 12 in. respectively from a conca ve mirror of radius of curvature 16 in.

An object. 4 cm. high is placed at a distance of 15 cm, in front of a cr vex mirror having a radius of curvature of 10 cm. Where will the image be and what will e its height?