1989-12-18 — Page 30

##

育 日一廿月一十年已己看夏

報日僑華

Find

2.

(a) the acceleration of the system. (b) the tension in the string.

(a) Let a acceleration of the system

T= tension in the thread

JON

2 kg

R 3 kg

1.

中華民國僑務委員會頒發登記證合敦新字第一一〇號

1990中學會考預習專欄

明德出版社

4. As shown in Figure 4, find the acceleration and the force between the blocks.

GON

2 kq

1 ky

WILL & DALE PRESS

6N

3N

Physics (12)

3 kg

1ON

·2 kg

Consider forces on the 2kg-block

10 - R 2a..... (1)

Consider forces on the 3kg-block

R 3a.....(2)

一期星日八十月二十(九八九一)年八十七國民華中 30)

Correction for Physics (11):

(c) if the cord is TOW slackened completely, the block is observed .to move up 5 meters further before coming to rest. With what velocity (just before stackened) travelling?

Was

it

Consider the 2kg-block

(1) = (2)

C. Y. Mak

Figure 4

Exercise 12 Force and acceleration (2)

(Take g = 10 ms";

1. As shown in figure 1, a system of 2 blocks 2 kg and 1 kg joined

thread together by a

is pulled along by a horizontal force of 60N along a smooth surface.

As shown in figure 5, a mass of 15 kg is placed 8 m from the edge of a smooth horizontal table and is comected by a light inextensible string passing over a smooth-pulley to a mass of 5 kg hanging freely. The 5 kg mass is 2 m from the floor.

The system 15 then released.

5.

SON

3 kc

kg

15hs!

60 T

= 2a

60 - 6 = 2a

54 T 2a.....(1)

Consider the 1kg-block

T - 1 = (1)(a)

5.

.*.

† - 3 - 8...........(2)

(1) + (2)

(b)

51 = 3a

a17 ms

7.- 317

T = 20W

-2

(Ans.)

(Ans.)

10 = 5a

22 ms

R = 3(2) = 6N

(Ans.)

(Ans:

60m

(a) let a = acceleration of the system:

after released

I tension in the string

Figure 3

15 ku

23-

Figure 1

十二月

Find

5kg

(a) the acceleration of the system. (b) the tensión in the thread

connecting the blocks.

2.

As shown in figure 2, a system of 2 blocks 2 kg and 1 kg joined by a

a

thread is pulled along by horizontal force of 60% along a rough surface.

Find

Figure 5

(a) the acceleration of the system. (b) the tension in the string. (c) time taken for the 5 kg block to

reach the floor.

(d) time taken for the 15 kg block to

reach the edge of the table.

*B

正地社穏

бота

2 kg

Figure 2

If the frictional forces on the

2 kg-block and the 1 kg-black are

4.

t*

話

A

更錦內灣台

ta

(a) the acceleration of the system.

4

***

6N and 3N respectively, find

(b) the tension in the thread.

3. As shown in figure 3. two blocks of masses 2 kg and 1 kg connected by a

light string is pulled vertically upward with a force 60N.

i

160N

Solutions to exercise 12

T = 15a..

(1)

(a) Let à acceleration of the system

T= tension in the string

(5)(10) - 75a......(2)

(1) + (2)

1.

50 = 20a

Fine in secord

-2

CON

a. 2.5 ms

(Ans.);

Figne &

2 kg

-2

(b)

T = 150

1 kg

ms

15(2.5) -37.5N

weight

weight

Solutions.

[Ans-)

(a)

Consider the 2kg-block

::

1.

Let a acceleration of the system

T= tension in the thread

60 (2)(10) - 1 ± 2a.............(1) Consider the 1kg-block

T- (1)(10) = (fl(a)......(2)

50%

(1) + (2)

3.g

50 - 20% 3a

-2

(1)(10)

T = 20N

(c) Apply S = ut + put?

- 2 = (0)(t) + }{2.5)(t)?

t2 - 1.6

t = 1.265s

(Ans.)

(d) When the 5 kg reaches the floor,

the string slacks. Hence the speed of the 15 kg block is given by

v = 0 (2.5)(1,265)

=.3.15 ms

-1.

(5)

the

Time taken for the 15 kg block finish the rest of

(a)

60. - T = (2)(6)

[[1]

(2).

3 44

(1) + (2)

6.0 32

2 = 20

(Ans.

(b)

$(20)

Figure 3

(Ans.)

1990 中學會考預習專欄

明德出版社

MILL & DALE PRESS

Computer (11)

40 FOR # 1 TO SIZE

50

INPUT DAT(1)

60 NEXT 1

70 REM GOSUB FOR SORTING IF

NECESSARY

100 INQUIT WHAT IS THE NUMBER TO BE SEARCHED": X

110

REM SEARCH FOR X

120

LOW,

130

GHZE

140

= INTL (LOW + HIGH)/2)

∙150 LE BATU

160

K.. Choy

170

we have study about binary search in the Flowchart section before. The coding

of binary search method (algorithm) into BASIC language is simple.

Suppose there are SIZE number of data in ascending order. (If it is not in order, the bubble sort algorithm and BASIC program on last wear may be used

to sort the numbers first.) We would like to find whether a number, X, is in the list or not. If it exists, the

position of it is printed.

BASIC program for binary search.

10 REM INPUT THE LIST INTO ARRAY

20

30

INPUT SIZE OF THE LIST"; SIZE DIM DAT(STZE)

X THEN 200

IF FC <.X THEN LOW = I +1

ELS HIGH = - 1

Á KOI HINH TIEN 40

180 PRINT "THE NUMBER IS NOT IN THE

LIST

190 GOTO 210 200 PRINT "THE NUMBER IN.

I

210. CND

Remarks:

(1) Binary search is a good systematic search algoritha. For example we have a list of friends and we want to search for his/her telephone number. This search algorithm can then be used.

(2) The data list DAT (SIZE) can be changed into character string. variable or any other meaningful variable name. e.g. NAME (SIZE}

4. Let R be the magnitude of force between the blocks, Ĉ be the acceleration of the system.

(3) The line 50 can be changed to use the READ.....DATA format or to be INPUT from files in the disk files.

(4) Line 160 may not be workable in APPLE-11 machine. It can be changed to

160. IF DAY(I) < X THEN LOW=1+1 165 IF DAT(I) > X THEN HIGH=1+1

There is no ELSE For APPLE-11

users.

String manipulation:

Computer-aided learning (CAL) 15 a valuable tool in the learning process. Write a CAL program to help secondary 4 science student to learn the names and symbols of the first twenty elements.

a) Starting at line 100) use READ statement to read the names of the

sto jelents into elementarray $12 nd their symbols into another array SYM$(20). The chemical names and symbols must be in the same order as their atomic number.

(b) [Starting at line 200) ask the user to input the chemical symbol for a chemical name. Store, the student's answer in a ANS$.

variable

= 3.164

Bad Time taken

1.265 +

(Ans.)

340

TE ANSS - VMDE

350

PRINT "THE „NGKOL OC

(c) (Starting at 1300) checking the answer ANS$ against the correct symbol. If the answer is correct, two marks is awarded. If the answer is not correct, print a warning message

the and ye student a second tra If the answer is correct. I agark 15 awarded. Otherwise correct. answer will be printed.

(d) (Starting at lineprint the

total score

twenty questions have been fin shed.

10 DIM NAME 2014 SYM$(20) 100 REM REBDOOREA ÎNTO ARRAY 110 FOR 0 20

120% READ-NAMES(20), SYM$(20) 130NEXT I

140 MARK - 0

200 REM ANSWER

210 FOR I = 1 TO 20 220

PRINT "WHAT IS THE SYMBOL OF

NAMES(1)

230

INPUT ANS$

300

REM CHECKING ANSWER

310

IF ANS SYM‡(1)

320.

330

INPUT ANSS

THEN MARK - MARK & 1: 3010 360

"

NAMES(1): 'IST SYSTE

360 NEXE T- 400 REM PRINT SCORT 410 PRINT "YOUR SCORE 5"; MAKN 500 DATA "HVORUDEN" "H"

"HEL TUR"

"

LITHIUM", "LA "BERYLEBAT". "Be

510 DATA "ROBON","8"

"CARRON", "C"

"NITROGEN", "OXYGEN" 40"

520 DATA "FLUORINE",

"NEON", "NO" "SODIUM", "MAGNESIUM".

530 DATA ALUMINIUM",

"SILICON",

"PHOSPHORUS".

SUMMAUR

540 DATA "OILORING

"ARCON",

"POTASSIUM"

"CALDEUM".

THEN MARK - MARK + 2: GOTO 360 PRINT "THE ANSWER IS WRONG,

PLEASE TRY AGAIN!"

the program can be modified to ask the do the other names in random number. hand, it can print the syanol and ask for the names, Try tins by varself,

今次到新加坡訪問,有機會門人才,應將前去工作,薪酬比,所以茶事多數女淡一 較優待,住公司提供宿舍,十分,否則「上加鹹」。近年旅遊

数日前難間短是勞工不足雖然

懲教客的防暴裝備,如難的到達,這無疑對戰勝,不但不幃餘職員的

·志偉對於··彼邦安居樂業了。 豬。因爲要參加中央公積金計 業興旺,估計新加坡飲食業前景 想適份依賴,勞工入口仍有些限

既可以輸入外地勞工,但政府不

。在-

滿緊戾的環境中脊。 摩頭盔、衛牌等亦不足夠良的生命热成莫大的咸 辛勞工作;反而不停萬 策劃船民的示成行動 染,把職員作為暴力的,這些可從傳單、橫額 更有外人交換協

不能超過百分逖十。他相信香港,沒有能力支持至支援部 的人士及假人道主義團 力執行鞦務,苛盧船民。

謝志批評越南 將船民送回港

蒴議

越南政府

LZÁM ER KA GIRL DEVERÁ CARLTON)

·劑,每月薪金百分廿二是被拍超 大有希望,他過魚有不少老·制規定工廠僱用勞工,外地的 如遇事故,廣員實在‘另一方面部份有心化身,增長百、擴香器等外來物传見

Contents

Meanings

1990 中學會考預習專欄

Economic & Public Affair (11)

Effects of Inflation

明德出版社

MILI &- DAUF PRESS

M. T. Kwok

Inflation is harmful to the salaried people and those with fixed punima, lies in the fact that their incomes remain more or less the same, but they have to. pay more for their livelihoods It also imposes ill effects on exports. the local costs. increase, the competitiveness of Hong Kong goods in overseas nurrets will reduce accordingly,

The reason:

C. Banking System

Contents

The Three

Der Banking

Systom

Licensed banks governed under

Banking Ordinance*

Meanings

Licensed Deposit-Taking Companies (LDTCS) for time deposits of HK$500,000 or more

Registered Deposit-Taking Companies (RDTCS) for time deposits of more than HK$50,000 with a maturity of more than 3 months

*Only licensed banks can accept demand and savings deposits and time deposits

which have a maturity of less than 3 months.

D. Inflation and Deflation

Contents

Meanings

Definition Inflation. is a sustained increase in the general price level. Deflation as a sustained decrease in the general price level.

inflation results in a decrease in the purchasing power of money.

De lation has the opposite effect.

However, inflation of a stable and wild degree may stimulate, une evenngry,

Inflation in Hong Kong

Contents

In accordance with the Hong Kong price index, the rate of increase was very low during th: 60%, being less than 4 per cent per annum on the average. However, the situation ringed greatly in the 70s, the rate of price increase (or inflation rate) attained two digits in 1972 - 1974. Though the situation became improved during the following years, inflation regained its neventum during the end of the last decade and the start of this decade, and the rate of price increas0 again attained two digits.

Angual Percentage. Change of

Consumer Price in Hong Kong 1962 - 61

1962 - 70

3.2%

1971

3.2

1972

5.5

1973

18.7

Types of inflation:

1974

14.3

(a) In creeping or mild inflation, the general price level rises slowly, (b) in walking or galloping inflation, the general price level increases at a

faster rate.

1575

8.0

1976

3.7

1977

5.4

(c) Hyper-inflation occurs when a very high increase in the general price level

destroys confidence in money.

1978

5.9

1979

11.2

1930

15.9

Causes of

1. Cost-push

1981

17.4

Inflation

1982

10.5

cost

Supply !

price!

1983

9.9

1984

8.1

2. Demand-pu!!

demand

3. Imported inflation

1985

3.1

price t

1986

2.2