1970-02-18 — Page 27

REFERENCE LIBRANI

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70英文中學會考試題預習專欄

主編

物理科(十六)

PHYSICS (16)

ANSWERS AND EXPLANATIONS FOR THE TEST

(D) 18

The rought of a bedy is measured by the product "of 20 maas and the acceleration due to gravity, zer a given mass er the same mass and at the Dwas pleco, where Imasa and e' ara bəli cənst their trigato Lust ko, the azas.

(3) is correct.

Kixotão energy - 1 x masa x velocity)"

34 ir avident that kinetic energy depends on mas znę velocity of the vehicle, The mass of the ves hidle is the game even though it is on the moon. Is it movsa with the same apsid on the moon as it is on the earth, it will posessa the esme kinetic crezay there.

(5) 19

aze pressure is measured by the product height of liquid column and its density or, for solid, measured by the ratio of

Freasure

force soting normally,

area

The minimum pressure means the greatest area in contact with the floor. The triangular arez ha an area of b unita, being the largest area of the five surfaces of the prism.

(3) le correct.

A hydraulic press works on the principle that 11- quid transmits pressure equally in all directions.

13.

(B) is oor of doing wOTA.

Power in the

Work done in raising the Body 550 x 4 ft-lb It is done in two seconds.

Therefore, the power - (550 × 4)/2 ft-lb/360

2 b.p.

(C) is correct,

the return of the ball to earth depends on tho gravity.

correct.

The smallest resultant of the two concurrent for. cen in the algebraio sum of two opposite forces. It is 8-6

(0)818

pd1.

Statement II is incorrect.. The point of appli- cation of the resultant may not act on the body. Statement IV is incorrect. If the forces are p parallel, their lines of action will propably no 20t be concurrent.

Statements I and III are the necessary and suffi- aient conditions for equilibrium of three or more. forces aoting on a body

de correst.

The centre of gravity of a body may not be with- in it. For example, tho C.G. of a ring. incorrect.

The centre of gravity is a point but not a force, (C) is incorrect.

"he centre of gravity of a body is a point that

117 not change in position wherever it is placed (D) ie incorrect.

E) is a statement to define the stable equilibriu if a body.

18 (3) is correct.

Ir tuo pali is placen on a seveż pinning swAD Boutral equilibrium. It it is inside a bowl, the -centre of gravity will be raised when slightly

displacod. It ia în etablo equilibólum,

LU) 18" ENDURE301.

force 10 noz a Eind of ener

(D) is correct..

By Newton's First Law or motion, the man will continue moving forward as the bus dosa. He tanda to fall in the same direction as the bus MOVER.

三期星日八十月二年〇七九一曆公年九十五國民華中

(接第七張第二頁)

鐵 中文中學會考試題複習專欄

F

英文科 (十六)

"None of them knew the answer, "No,

"He's been living E

"Yes,

"She'11 help us, "Yes,

a long time,

We mustn't forget to remind them,. "No,

j)"He shouldn't have said that,

"No,

ANSWERS TO PREVIOUS EXERCISES EXERCISE. 18

(a) favourite. (d) informed. ()seriously (i) property (n) torn

profession clothe

EXERCISE 19

(a) bill.

(d) food

(z) balance

(3) There

strolled achieved genuine

account (1) wish (1)

progress

lay

illegible

(k) used

incredibl occasion should like

(b) uninteresting(e

evidence. abolish

200

Coldius and Fehrenheit Scalea

Scale

Celcius

Fahrenheit

L.F.P

scenes

friends

rec

hard

U.F.P. DEGREE

between fixed-

100°C 100 degrees

212 B 180 degreen

Froblem reastures | Conversion ci sonima) Problems in thermomstry Sffen reduce to exercises in converting temperatures from one acale to another. These should not be thought of as requiring formula for the solutions, but should be solved on the basis of a knowlege of the nature of the temperature scales Realizing that that each Fahrenheit degree is 5/9 ( Eame de 100/180) the size of each Centigrade degree, and that 0°C corresponds to 32 F, conversion problems should be handled na a simple proportion arithmetical problem.

(C) is correct.

Let V be the volume of the mixture. It is made up of two substances of volumen 1/5 and 37/5. Their masses will be 4 x 27/5 and 5 x 37/5. Their mkasos whèà háded - 237/57

The specific gravity of the mixture will, thero- fore, equal to 23/5 or 4.6.

A) is correct.

They apparently lose the same weight and therefore experience the same upthruat. That is, they dis- place the same volume of water. Their volumes are equal,

is correct.,

WŁA SWOBOlia spheres naye the gate vojuZLERE MADE GA displace the same amount of water. The one with 5.0. less than unity floats, while the one with 3.0. greater than unity sinks.

(B) 18 correct.

The force of attraction between the water molec- ules anabihasmolecules of glass makes it diffí- cult to lift the glass ups

HEAT

neat and Temperature

Teat is a form of energy. Temperature is à moasurement of the degree of hotness and coldness. It does not measure the amount of heat

body containa. Temperature, is qualitatively speak- ng, a property which governs the direction of flow of heat. The temperature gradient determines the dir- iction of heat flow, i.e. heat flows from regions of 1igh temperature to regions of low temperatura. Thus

eat and temperature, are not to be confused. The easurement of heat and that of temperature being ntirely different procedures,

*3#51C T28ow of kattar

The material in this paragraph is in- material to the Form 5 syllabus. It La included here primarily to enable students to form metal pictures of some of the con- cepts which follow in the study of heat.

100

180

Example 16 —

to - 40°C

What Fahrenheit temperature corresponds to * 4

40°C is 40 Centigrade degrens below the free- sing point of water. Now 400 degrees 9/5 x 40

727 degrees. But 72 F degrees below the freezing point of 32 degrees ♬ 18 407 degrees below °F (72 - 32 - 40). Thus - 40°C — — 40°F.

The problem can also be solved by letting

Types of Thermometern

(E) is correDE.

The time taken for an object to fall from a certain height is independent of the mass and

(E) is correct.

Initial velocit

Acceleration,

"TIME" TAKO

20 ft/sec

1 32 ft/sec.

Applying the equation of motion.

ná + at

The velocity after 3 second is

➡ 20 + 32x -36 ft/sec.

(A) 18. Correct,

Velocity, kinetic energy, momentum and power depend on the speed and consequently on acceler ation. Since acceleration of the bus is uniform, ita speed changes from time to time. (B) to (E) are false statementu. Mase is the properties of inertia of a body. It is constant, and is ine: dependent of acceleration,

(D) de correct.

Vistance travelled:

$.

-10 ft/seo

five seconds, it travels

- 1 x 10 x 25

125 feet

Nattara are made or, molecules, atoms, elctrons, pros Tons, add neutrons. The atene is the smallest unit of a chemical element; the molecules is the smallest unit of a chemical substance or compound. Molecules are in a state of random motion. In the gasous state they have considerably more freedom than in the li- quid states, and more in the liquid than in the solid state. The total energy thus Beociates with the ràn- Asm motion of the molecules of the body.. In other w words, the addition of heat to a body increases the thermal agitation of its molecules. Temperature is defined as the average kinetic. saergy of translation of random motion of the mos

Effecta oF HOSTINS

when neat is added to a body, it may result in pro- ducing one or more of the following effects

increase in temperature,

(2) expansion

םמם חיים מור!

change in states

change of chemical consta tution, change of electrical properties, change of colour

There are many thermal properties of matter, but simple linear expansion is utilised in the mercury- in-glass thermometer, in which the mercury expands from the glass bulb. into a connected glass capillar tube, Two temperature scales are in common use, th Centigrade (Celsius) and the Fahrenheit, both related to the Fixed Pointa : The Upper Fixed Point-

Ane Lower Fixed Point

They are

the temperature of the steam t normal atmospheria prese ure, 76 on of mercury.

the temperature of pure:

elting ice at normal atmos pheric pressure.

Liquids used: comarqury. alcohol advantagest

simple:

(2) easy to assemble

direct reading'

can be modified for special usag

isadvantageut

"unauitablā” for high temperature unsuitable for low tempert:lurz reading depends on the leng making the column teo. Len, sensitive ty- dapénda on

featuresï

Vieng thannonatayu are made more sensitiva by a Larger bulb and a narrower capillary tube. Unless. %5 device is to sohieve a quicker reading and the therus metrio liquid has a vody low specific heat, is usually made large,

no100 or 1iquia for sAermoneters/

savamune trio liquids should have

s high boiling point

a low melting point:

#paque

does not waï the glass wALL

(5) regular expansion

quiok response

low specific heav

lèw specific gravity

large' coefficient of expansion

Bulb

Clinical thazuoneter has a very anali range, in vazi sensitive, and retains the reading until shaken, rentziation is necessary to pravdat, the expanded lic uid in contracting. ghe aten da triangular to magni- f the mercury column, as the effect of a long,

(aximum and minimum theraonster in used to record the saximum and minimum temperature of a prefixed range af time.