23 MAY 1967
(=#BIRGITY HAILORSTAY
育收僑華
英中會考物理科答案(菸)
HONG KONG ENGLISH SCHOOL CERTIFICATE EXAM.1967
Suggested Answers to Physics,
Section B.
4(a) Various substances do not expand equally when
their temperatures are raised. Their properties in this respect are expressed by the coefficient, of the linear expansion, which is defined as follows.
the coefficient
of Linear expansion of a sub-1
stance is the fraction of its original length by which a rod of the substance expands por degree/ rise in temperature van
The coefficient of linear expansion of steel/ is 0.00001 per means that for each degree centigrade the temperature rises the length of of a steel rod increases 0,00001 of its original] length.
(b) Assume that there is a cube of steel of side
1 om. If this is heated through 1 deg, centigrade the side becomes ( 1 +α) om where 0.00001, and the new volume is ( 1 +X) - 2+3x+307α 8.0. Since is very small, neglecting the termso and we obtain 3d where Y is the coet-^ fiolent of cubical expansion of steel
Y. 30.00001
0.00003
perc
per
(c) Leto be the original length of the circumferen-, ce of the hole, be the length of the ciroun- ference of the hole at t C
∞ - 0.00001, t = 500°c
percentage change in the circumference of the le «, increage in vlength/ original value
0.00001 x 500 0.5%
increase,
Letv be the original volume of the diso, be the volume of the diso at t
• v( 1 + 30+ )
percentage change in volume -
5
inoreas)
pheréo - prESSUTO - 30.
re of the mercury column
turé - 27 C
abg.in. be the cross section of the
oyle's Law PV» F_V_ when the tem
kept constant..
WAH HU YAT PO
N.B. The Length of the column of gir is pro-
portional to the volume since the Cross- section of the tube is uniforme
5(a)(1) Thermal capacity: The thermal capacity of al
body is defined as the quantities of heat re-.
quired to ralle ita temperature by 1 deg. Themal capacity 18 related to specific heat by the
formula thermal capacity-specific heat.X mase. (11) Latent heat of fusions Substances changing From the solid state to the liquid state absorb heat, but the temperature remains unchanged,
Therefore, the latent heat of fusion of a sub- stance
nce is defined as the quantity of beet re- quired to convert unit mass of the substance from the solid to the liquid state without change of temperature.
(b)(1) We use the method of mixtures to find the ⋅
specific heat of lead shot. This can be found by warming the lead shot to a high temperature and then quickly transferring it to a calori- meter containing cold water, The water and calorimeter receive heat from the solid and al}} three finally reach the same temperature,
fairly large amount of lead shot la put: In to a test tube which is put into a beaker of water. The water is kept boiling by a bunsen burner. We have to find the thermal capacity of the calorimeter before-hand, The result may be obtained by the following calculation: Weighings.
lead shot
calorimeter
Balorimeter and waters k
Temperatures.
hot lead shot
cold water
mixture
gm..
b
Thermal capacity or the calorimeter and stir
■o cal./
Calculations.
specifio heat of Water - specifio heat of lead shot -
Heat given out by hat lead shot
gm/degt gdeg
cal.
Heat reversed by water
b) 1 x to Heat given out by hot leden
c21.
Heat recen and calorimeti
nal/g/degC
cooling.
protect Jetting
ced
日八十月五年七六九一曆公年十五國民鞋中
梭學科專商文立官
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校分立設區龍九在能可
加增有大牌額學年學下
TIGERM
PEAK
G-IGE-EX
秒收益者,屈時可留我用胞。 七月初噐始师理科生,至於今秋入該後寫團聚九十四名! 葉良新生工作,官立交商本校亦將 鹃生六十二名,二年 <<<TEMOSIESENEST KKR – WEET (CTE) MAKMAFODEN LEK+1}<• #E TEWEK KU
羸,今年仍難收文科一年級新生及 RAE DEL SO THE ME A HOT - MARGIEL 文科征第一年破一年以上带有出,該校擬於下學年在九 三年級,看在認可之大華或本科離校西可能太有增加,因 凡中文或英文中學會考及格者(本年又撼贷近方面强 KERSERESSEN ) NAH
SALAKET VERSI
IN PRENTE ENKLE
外匯史、鄭經選讀等 學生車牌號讀。百分之八十,而龍
ENGINE BATEIN- &SERKACIEH
-12-195-EE E-MSCHIKTIREERS 哲學衙論;三年級官 篌亦成有若干低聲學,無該校公佈,去年 近代史、杜斯小區威厚費。此外,該惠的兒龍峰國中很多來電話。鋼者 運史、社會學二年級社1回究,英文、中國文學,亦無選 拓、中國新學、中國 格後,可申【發識所 致師,故花年由跟 成君:有耍 KEKET (2) 女商各科,近年則上图文科一科:新校秘之,亦 PREISIL-RYE.
「我 了解各校官小節,世有申請 優荐,並阿武县北檔 烹製會,展開相的四名,其中男生有 要職教師何况由校長升般爲「文焘激師一百万十二名增加七十
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REL
第
注真四息有 意
(6)
刊 教
在
PLANE MIRROR
REAL IMAGE.
OBJECT PIN
2
如果行,則九龍區之 關作九祖分校。事
(Fig.);
EYE
The pin is set vertically in a special carrier held by a retort stand. Having adjusted the pin so that its tip is at the same horizontal level, as the centre of the lens a position is found for which there is no parallar between it and the real image formed. (Fig). Attention should be given to the tilt of the plane mirror so that the tip of the image and the tip of the object pin appear to touch at the same level as the centre of the lens. The distance between pin and lene will be the focal length of the lens. (0) The formula 18 1 13 1
where is the distance of the object from tha lens, vis the distance of the image from the lone, and f in the focal length of a lens, $11 distances are measured from the optical cen-
tre. Distances of real objects and real images are positive. Distances of virtual objects and Images are negative. The focal length of a com vorging lens is positive and the focal length at a diverging lens is negative,
a) Since the path of 1fght le reversible, we can take the image distances to be the object dis tances and vice versa to obtain more points on
the graph
the dry air in A
the dry air in B
the dry air in A.
the dry air in B
32 x 108
x 10
ou
(1) Diagram 3 and c show that the pressure of
the dry air renains constant, By Charles Law, V/T
on.in
273+ 27 °K 300 K
10a ou.in.
ou,in.
required temperature in diagram
in Kelvin.
102 1300
1120
262.5 R
262.5 -273--10:5
air in
length of the oelumm 023 ram B is 1lege in
(11) The column of air will return to its original length of 10 at 60-10.5 0 when the tube remains inverted Set up the apparatus as shown in diagram B. Re- cord the atmospheric pressure and the surr anding temper ture and measure the length of the mer- cury column as well as the length of dry air. Now the pressure of the dry air is equal to the diff ence of the pressures of the atmosphere
the mercury colum13; 128 difference is always
ort period of time. Then change
emperature of the dry air by
water bath and record the new
bestem vera.
apes
is experim
10)
temps
bo11
maus: oʻs
latent heats
Heat given out by
quid oxygen.
sphere 80x0,1x(20+180)
Beat received by oxygen, — 10L
1600%
cal.
cal.
100 1600
L 160..
oal/gm.
Answert The latent heat of vaporisarten
liquid oxygen is 160 cal
IBR
than
(d)(1) The slope of the curva at A is greater, that
at C because the temperature difference at A. 18 greater than that of at C comparing with the room temperature, From Newton's Law of cooling the time of cooling near A is shorter; than that near C.
(11) From the graph QR is a horizontal straight
line. This means that the temperature from Q to R remains constant. This is possible only when the naphthalene reaches its melt- ing point 80 0. The temperature will not change until all the naphthalene has solidi. Pied. Although heat is steadily being lost by convection and radiation all the time, The heat loat is exactly compensated by the latent heat of fusion of the naphthalene, which is being given o
given out during the change From the liquid to the solid state.
Section
6(a) The principal focus of a convex lens is that point on the principal axis to which all rays. parallel and close to the axis converge after passing through the lens.
Principal forus)
Converging lines.
Distanca of image, from
10
10
20
30
40.
Distance of object from lens. (Cms;
From the lens equation
if vu, then
From the T that
21
+
can find a value of u such value is when u-v-30
15
By calculationi Brom 1
fo
a real image:
:20 Om
ABD'
th of column
of dry
and fin of air
o is pra
of the
All the values can!
Length temp.
•
fecal Lough
The centre of the lens de called the optical. centre The focal length of a Lene is the dis-) tance between the optical centre and the prin- cipal focus. Since light may pass through a lens an either direction,there will be two principal fool equidistant from the optical centre, one on either side of the lens, Therefore there are two focal length of a thin lens but they are equal
a virtual imager
u-10 cm
Answer: The distance of the object from & conver
lons 18 20 cm. for a real image, and 10 om for a virtual image.
To be continued!
Page 15Page 16
一。因爲在同一時間內叉插頭通第三號不同 · 露無用。
麼殺過靜與所能負担的,便會出事,例如洩花、壢年