1968-06-01 — Page 22

日六初月五年申戊麽

WAH KIU YAT PO

Vpayer In n temperaturo (if any) recorded by the four themesnatayer/272) Cand Defter switching on the two heaters."

蒸中會考物理科試題

ងអបរំចង

Time allowed Two hours and thirty minute

Answer FIVE questions, choosing at least ONE from each section. Mathematical) Tables will be supplied. Graph Paper will be supplied on requests

SECTION A

(a)

Stato the principle of Archimedes,)

(b) A rubber balloon has enough hydrogen pumped into it to make it vise frema

sea level, Use Archimedes principle to explain why te rises, and why it will only rise to a certain maximum altitude. Assume the temperature ie the same at all levels,//

Fig. (1)

2008

Fi. (H)

Smooth pulley

Liquid

Fiz. WD!

(<))

Give reasons for the shanges in temperatura which you hiwa kulitentat)

· A 1 KW power delli-lo sued to porą sinhill holes la a Vioon - light alloy having spaelfie hest

-1, 2'uatortom ġmi deg. Cand muss 2 mg

(assumed consthat throughodej

If 70% of the power in man goes towards heating the metal blocka find how long it would take to raise the temperatura of the blocke from 20°C to 60°C.

(The mechanical equivalent of heat » 4.2 Joules gaiarie pf)

mase of water per minute, starting at 70°C, and trickling over the block, will just prevent the temperature rising above

40°C+

() Define the ternis latent heat" and "Latent heat of fusion of Ita"!

Density of waters

Igm/co/

(b)

Fig, (iv)

Draw a volutnie temperature graph indicating the changes in volume which? takes place when I gm. of ica la warmed from -5°C through its melting point up to 10*C«. (Take 'voluice" as the vertical axis,);

AU-tube containing water at room temperature has part of one arm" surrounded by freezing mixture as shown;❤

Write a brief account of an the

changes that will take place in

the tube, and give the reason":

for each changeę.

Freezing salxture

台一月六年八九一番公寜智

KAT Draw a labelled fingram of a Daniel Cell. Explate what happend et Tko'

morface of the copper electrode of the cúl1, - What passes through th

YOUR DO12). What happens at the surface, of the zinx ród?

10 ohma

*10 ohme

Two Daniel Cens are placed in series and are connected a voltmeter V of very high resistance as shown in the diagram. The reading is taken,. and then the switch A is closed as as to connect a 1052 resistance in parallel with the voltmeter. The reading then falls from 2.2 volts to Z volts.

Explain carefully why there is a tan in the reading on the voltmeter," Caucusate what the new reading would be. If switch B were now to be clored so as to include a second 1012 resistance in parallel with the firs

A LOR VOLT, 23 warr ngnt buto and a 200 vait, so wat night aird are connected first in parallel, then in series, with 200 volt supply. Describe in gen ral terms what would be sea,

Calculate the electrical energy which would be qonsumed in each casa1 within one hour. Assume the resistance of light bulba to be constant whether cold ar háil.S

➜ wooden block is weighed in air, water, and liquid X, na shown In Figures (1)^(II) and (iii) above. "Finally a lump of metal:UM" with density 10 gm; per co., lạ attached to the wooden block and causes (t to font inwater with its upper surface level with the surface of the water as shown in Fig. (iv). Use this information to; find:

((AE)·

the upthroat on the block in water.

the volume of the block

(iii) the density of the block,

(iv)

he density of liquid *X",

be mass of metal lump, "ME

Piens's turn overz

lete

For all calculations in this question, use the approximation g = Afr resistance should be ignored.

(a))

1000mg/s

A Blue pronium Un, of length 100 cm, Is" suspended at a point 0, 130 cm. above a bench top BC which is taken as the reference level for calculation of potential energy, Thé bop. A of the pendulum weigha 20 gm, and is drawn aside until It is displaced 60 cm. horizontally from its equilibrium position. It is then released and allowed to oscillate freely in a vertical blarin

Calculate:

(lv)

its maximum potential energy, Ita minimum potential

energy,

ita

a maximum kinetic energy, ite maximum valocīts

Describe briefly how you would set up and use a simple pendulum to find

value for the acceleration due to gravity, making one determination only. Include in your description all precautions which should be taken,

wody un chass ag rests with its c. g. 40 cm. from the edge of a frictionless table sa shown in diagram. It is acted apon by a steady horizontal force of

5 gm. w, until its C. g. reaches the edge The body then strikes the floor 0,2 šesom after commencing to fall

(b)

the acceleration of the body along the table for

the time taken for the a. g. of the body to reach tas the table,

filt the boyfcontax distance travelled by the eag. of the bolly 6, 2

vecond after passing over the edge of the table,"

(iv) - the vertical distance travelled by the d. g. d the body, 0, 1 second

after passing over the edge of the table."

Cotton Wool

In an early biologivas coporument on Crushed metaboliem, a guinea pig was enclosed

in an insulated wooden box with kilo gram of dry, but melting ice. After a period of 4 hours the box was opened, and was found to contain just water th addition to the guinea pig, and that the water had now attained the initial hody temperature of the animal, 30 Ca Assuming perfect insulation, and that the latent heat of fusion of ice is 80 cal/gm, calculatete

(1) the number of calories per minute

produced by guinea pig.

- the power in watts that this

representeerin

day

SEKSE Turnover,

A strong permanent magner trops through a solenord which is short; circuited as 'akowa.

SECTION C

Define 'refractive Index”

Draw a diagram to "how way in object lying beneath water appears to ba nearer to the

It really is.

A fish lies at point 8, 5 fout y below the surface of clear water, as in the diagram,. A buy whose ayo level is 4 feet above the ground stands at P, 3 feet from the sige of the pool. If the refractive index of the water is

find the greatest value of RS-

Tish will not be sean

(by the boy

Position 2

Magnet Appro

ching)

Position A

Draw carainliy labelled sketches to linstrate in Each of three

the direction of any current flowing. (11)" the polarity of the solenoid,.

[ili} tha magnetic fields of the magnet and solerome

Stats Faraday's decond law of Electrolysis, and dess to verify the law for the metale silver and copper.

Acidulated water is electrolysed in a Höllmann a with a copper voltameter. If, during ane hour" oxygen is released,

5(a)

Crate Boyle's Law,

Borcury

Vignet

apillary tube"

TION

Horizontal and.

Vertical lines drawa 'st'em, and mm.

spaces

plate

Ray

In the above apparatus; « unzzozm naztów tube containing dry aix trapped by a column of mercury can be fixed in any required position to a vertical tron plate by permanent magnets, Show how the apparatus could be used to verify Boyle's Law from observations taken with the tube placed in horisontal and vertical positions, (Barometric height = 76 cm. of mercury)

Explain with a diagram how the same apparatus couin be used to obtain more than three readinia to varite Bevlala La

graphs you would obtain if your readings were plotted as 7 volume against pressure

me against

(In both cases, plot volume on the vertical aviak)

Mercury

A uniform tube, saaled it ona una, containing" dry air in lowered beneath the surface of mercury as shown in the diagram. If the atmospheric pressure la 75 cm. of mari find:

(1) the pressure in the mercary at levelTMÄ

the Isngth of the kibe,

the depth to which C must be lowered

for the volume of the enclosed air to ba reduced to phe half of its origħal volume

souw a circuit diagram iṇātealing now you woura determine, by añ electrical method, the number of joules which Ard équivalent to ona d calorie; you can assume that a standard ammeter and a standard voltmeter; are available. List all the readings you would make, and indicata (using symbols) how you would calculate your result.

60%

ray of light strikes the face-A-B-of-a- *10* prism normally as in the disgram.

If the refractive index of the glass la L5, show that the ray will emerge from

the prism after being deviated 60* from Its original direttion.

If the glava priam la replaced by an exactly similar prism of a different material, what is the refractive

of this material if the rhy tatt ema from face AC?"

UBLICY

(Atomic weights of hydrogen, oxyge and 108 respectively. The electro-ch

000338m per-realomb, Hydrogen and pil and copper divalent).

Gabifidáte. Number

Answer this question on this page,“ then tear it OUT of the fuestion.. Book, and attach it inside your Answer Book,

Tura the page sidewaysA

focal length

A convex lens ls used to form images of an erect object placed on the axie at the points marked A, B and C in the diagram. State at which point, the object should be placed in order to form

(1)

real, started and duratalshed image.

(15) » virtual, erect and enlarged image.

By accurate geometrical construction draw full #dale diagrams to show

how a convex lens of focal length 4tros can form

(12) ma vietuas linage.

twits the size of a given öbjaðr óf height 1cm),

A kompozos ditersscope consisting of two convax tenses only in used to examine a "comil döjecta. Drawá rough-ray diagram to show how the finál Image is formada

in a model compound microscope me gojective xens and the eyepiece baver". focal length of lem and fems respectively, and taby are 11ème apart. An object of diarretas Emm is placed at right angles to their common uzla at a point 1, 2cm from the objeětlva 18ÄRJ

Calcula!

(i) the wizeldot position of the tinage rozmen by the objective per (14), the cots) dinner magnification produced by the whole, ioätkument

Rame the nigh convention you are aside for your calculations,

(ii) Indicate a rarefaction on the diagram.

(iii) Indicate one wavelength on the diagram,

Indicate a compression on Ae diagram,

(iv) Indiente on the diagram the amplitude of the sound wave.

„sound wave passes through air, (b) the displaced positions of the same molecules as a

„NOW_TURN-OVER

The magram snows jay the positiope or COBBLY Spacca Morguja in still air.

1121

Explain briefly, in the spaces provided below the e Increasing the loudness of the found would have on numbézöd 2, 7, 11 and 13.

upaca filled with

Particle

How are the phch snk séuɑnése of a note controlled in a krelaxed musical Instrument sŭcă da à guitar? -

plain briefly way the same musical hõta sõunds Bufferently when played on different musical instrumanía

Partiola

simply why a louder náte is hḍarg wom a tuning fork If it ip Heim so that it hafiets kuthol = labia töpe

Particlo 111

A thermometers are as room temperature before the £43ão Lille sham Jantored

moen in copper, and a thin-walled cylinder containing water having the

were heated by identical could as shown the diagram. hipzatiwa doanke og the same set of xxAR LO

tidernag dad bl 128 fork is Béla OVER 1B8pén end of ma auítaly-Loma tibe Knieh tu alaska së: the other end.

Why should a. «#cond gylinder, which ta langir, aíná pródúéā”

Loud aute

Particle 137