REFF
RARY
2 OCT 1970
育教僑華寛三第張六第日九廿月九年戌庚
報日僑罩
WAH KIU YAT PO
Unstable equilibrium
1971 英文中學會考試題預習專欄
(ii) Neutral equilibrium
新光出版社主編 SUNLIGHT PRESS
物理科
PHYSICS
LESSON ONE
A body is said to be in unstablë equilibrium if it. moves to another position when it is slightly displaced and then released
A body is said to be in neutral equinonum o remains, in its new position when it is slightly displaced and then released
43) MOTION-
(a) Displacement is the distance between the initial and final points of motior
ncheding the idea of direction
三期星日八廿月十年〇七九一公年九十五國民蔽中
(七一年度
中文中學會考試題預習專欄
英文科
LESSON ONE ENGLISH LANGUAGE
28th Oct 1970
(b) Velocity the rate of displacement
5 • displacement
uniform.velocity
time
This series of revision tests is prepared for students sitting for the subject of PHYSICS in the Hong Kong General Certificate of Education Examination (English).
The aim of
These are meminations is to test attainment and avility.
in terms of marks scored at an examination Every candidate must therefore am at writing solutions which wil earn high marks Working through exercises and
and questions similar
to those set by the examiners is one and indeed may well be the best way to gam this experience It is precisely for this purpose that the present series of revision tests has been prepared
The Syllabus for this subject is quoted for your reference
(A) GENERAL PHYSICS
1 Mass, length, time and their units The Metric system
2 Simple measuring instruments
3 Mass and weight Time 2nd its measurement Earth's gravitational
3
traction.
4 Force, Rectilinear motion, Inertia. Momentum.
S Density, Principle of Archimedes Flotation
6 Moment of a force
7 Centre of mass. Parallel forces. Equilibrium.
8 Vector quantities
9 Work Energy Power Conservation of energy
10 Machines and the Principle of Work
1 Friction
12 Pressure in gases.
13 Pressure in liquids
14. Particle nature of matts.
~(B) HEA",
45 Thermometry
16. Thermal expansion
17 Thermal and mechanical energy
18. Change of state
19 Transfer of heat energy
(C)WAVE MOTION LIGHT AND SOUND.
20 Wave motino
21 Properties of waves
22 Electromagnetic waves
23 Light waves
24 Rays
25. Reflection.
26. Refraction at plane surraces
27 Refraction at spherical surface.
28 Sound waves.
29 Air columns
30 Stretched strings
31 Characteristics of a sound:
(D) MAGNETISM ELECTRICITY AND ATOMIC PHYSICS
32 Elementary magnetism
33 Electrostatics
34 Celts and Accumulators:
37 Electromagnetic induction
35 Current and its magnetic errec
36 Units. Simple circuits.
38 Heating effect of current
39 Chemical effect of current
40. Instruments
41 Cathode ray:
42 Radioactivity-
43 Atomic structure.
IMPORTANT DEFINITIONS AND EQUATIONS
(A) MECHANICS:
11 FORCI
(5)
Vectors are quantities having magnitude and direction,
acceleration, momentum etc
(b)
(c)
The Law of parallelogram of forces.
"Acceleration is the rate of change of velocities.
at2.
PAPER 1. COMPOSITION | FIMES ALLOWED - 2 HOURS)
An English composition of about 150 words On a simple subjeci or topi
160 marks
Letter writing. The content is not to be less than 50 words
(40 marks)
final initial
acceleration or retardation, in the latter. case a is negative time
PAPER II
d Equations of Motion
2_aS.
for uniformily accelerated motion:
at.
5- vf ——→→→ for uniform motion (ie, no acceleration,
(e). Newton's Laws of Motion
(i) Every body will continue in a state of rest, or of uniform motion in a straight
line, unless it is acted by an external force
The rate of change of momentum is proportional to the force acted and fakes. place in the direction in which the force acts. momentum product of mass and velocity The rate of change of momentum = Ema
my mu
ma.
=ma when is expressed in absolute units (ie dynes, newtons or pou
iii) To every action thère is an equal and opposite reaction.
f) Conservation of Momentum
When several bodies act upon each other, the total momentum remains constant provided no
forces are acting
The weight is the attractional force exerted by the earth on the body. Sinë. = ma, the acceleration produced due to attraction of earthis s W mg.
he weight of the body depends on g son varies from place to place since g changes from place to place being greatest at polar regions and least near quatorial regions.
The mass of a body is the quantity of substance in the body 11
4) ENERGY. AND MACHINES
Work is defined as the product of force and the Unstanc
direction of the force.
WES Cus-0
where 0. = angle between 1 and
The unit is in joules or 11-b
(b) Power is the rate of doing works I
ES
the units of power are. watt (jouic/sec)® the units of power are horse power (550 ft-lb/sec.) Energy is the capability of doing work
Potential energy, is the energy possessed by body by virtue of its position PE mgh
Kinetic energy is the energy possessed by a body by virtue of its motion K.E my
Conservation of energy states that the total energy, in a given system is always constant or tenergy in a system can be converted from one form- 10 anothar but no destroyed nor created
load cfort
te) Mechanical advantage a defined as
-1)
"The "slistance moved by load-
Velocity Ratio is defined is in distance moved by elton velocity ratio of
single string pulley system.
rength of plane (ll) inclined pàng ạ
height of plane
radius of wheËI radius of axle ircumference:described by the sandle of length i pitch the vertical distance between two consecutive threads in the screw)
no: of cutieys which the string passes over
cose, 8 8 w the angle of inclination of the planc
(iii) wheel and axle:
(38) Screw, Jack
(v) = Hydrauli Press.
Area of large piston (the piston where the load is placed): Area of smaller piston, the piston where the effort is applied)
velocity force
(vi). Lever
(g) efficiency
effort arm load arm
Outpul
Scalors are quantities having magnitude only, eg density, volume, mass.et
If two forces (vectors) are represented in magnitude and direction by the adjacent sides of a parallelogram, the resultant is represented by the diagona. through the pout of intersection of the adjacent sides.
(d) Resolution of vectors.
vector can generally be resolved into 2 components, one being perpendicular to the other
horizontal component=
vertical component = F sin
The Law of Triangle of force
If three forces, acting at a point. Can be represented in magnitude and direction by the sides of a triangle taken in order they are in equilibrium
48) » Conditions of equilibrium of several coplanar forces acting at a point.
(1)
Algebric sum of vertical components 0
(i) Algebric sum of horizontal components : 0
[(2) MOMEN”,
(a) Moment of a force about a point is the turning errect of the force about that point is measured by the product of the force and the perpendicular distance between the point (usually known as pivot or fulcrum) and the line of action of the force
(b) The Principle of Moments
When a system is in equilibnum the sum of clockwise moments about any point is the same as the sum of anticlockwise moments about that point A coupleA pan of parallel equal but opposite force ÏA couple always
produces turning effect, though the resultant force is zero) d) Moment of a couple is measured by the product of me force and the per
endicular distance between the forces
Conditions of equilibrium of several coplanar forces acting on a body
(3)
Algebnc sum of horizomal forces = 0
(ii) Algebric sum of vertical forces 0.
(i) Sum of anticlockwise moments about any point in the system that of
clockwise moments
Centre of Gravity of a body is a point through which the total weight of the
ody act
g) States of equilibrium
Stable equilibrium
A body is said to be in stable equilibrium if a retunis to its original position when it is slightly displaced and then released
Tomut
h) Principle of work (1)
(ii)
Work cone by effort
Mechanical advantage.
Work done by: load Work, done by effori „Velocity, ratić"
For prelevt machines
Work done by load * Work done by ellon, For ordinary machines.
Work done by load Work done by movable parts of machine Work done to overcome.fratIOR
51. FRICTION
(a) Friction is the force opposing motion. '11 depends on the normal.
body and the nature of surfaces in contact
Coefficient of friction is desined as
ormal reaction.
Angle of friction is the angle of the inchnation of a plane at which the body placed on the nuine will dule down the inlane with uniform"
161 PRESSURE
Pressure is defined as the force per un area P In the case of liquid pres
sure it may be calculated as the product of height of liquid column and the density of liquid.
Pahd
(b) Boyle's Law For a fixed mass of gas at constant temperature, its pressőre ú
inversely proportional to its volume
Pascal's Principle states that liquid transmits pressure
(7). DENSITY AND ARCHIMEDE'S PRINCIPLE
(a) Density is defined as Mass per unit volume
(b) Specific gravity of a substance is the ratio of density of a substance to that of
Mass of a substance water. S.G.
Mass of equal volume of water S.G is only a number
(c) Archimede's Principle states that the upthrust experienced a body totally or partially immersed in a fluid is equal to the weight of the displaced fluid, y
The upthrust apparent loss wunauwi un fluid F
(d) Law of Flotation states that the weight of a floating body is equal to the
weight of displaced fluid
Since weight of the floating body in the fluid is zero, and by Archimede's Principle'.
wt in an -win fluid wt of displaced fluid
wim art of displaced fluid (for a floating body..
30% of the total marks should be allocated to this paper
GENERAL ENGLISH TIME ALLOWED
2 HOURS) Questions on Enghsh vocabulary and usage to include the following
RE TO LOW
Vocabulary tests - the right spelling of
words. the choice of the right words to be used in a given text, synonyms and antonyms
etc
The nent use of tenses.
The right use of prepositions
indirect and direct speeches.
Combination of sentences.
Negative, affirmative and interrogative sentences.
30% of the total marks should be allocated to this pape
PAPER III: COMPREHENSION TEST AND TRANSLATION
TIME ALLOWED - 2 HOURS)
(a)
Comprehension of a given passage of English. prose Questions will be set in English on the subject matter contained in the passage and ans wers must be as far as possible given in the candidates own words.
(30 marks) Translation from English to Chinese of English passages containing simple common idioms and totalling from about: 100-150 words
(30 marks): Translation from Chinese to English of Chinese passages totalling from about 100-
•150 words.
(40 marks)
الشعر
-30% of the total marks should be allocated to this
paper
CHAPTER. I
COMPOSITION
The two essential conditions in writing a successful composition are
Its material must be arranged in a natural and orderly manner
o make a satisfactory essay, It is essential and necessary to arrange your ideals of facts according to some orderly plan. Without it, your essay will be disconnected, rambling, disproportioned and full of irrelevancies and repetitions. Thus you'. must decide on the live of thought to be followed in the essay, a natural, logical and convincing order in which you must arrange the thoughts you have selected. The essay will be clearer and more coherent if all the material relative to one heading is included in the paragraph dealing with that heading.
ed in the paragraphy
Conunuity of thought must be shown in It!.
The thoughts must be continuous, that is, there must be no gaps nor jumping from one idea to another. Each idea must lead on naturally to the next. Similarly, each paragraph must be the same. The thought expressed in the essay must clearly have a beginning Introduction there must be a substantial body of material to constitute the middle- the Body of the Essay and n must have a
successful ending
Conclusion An abrupt or a feeable ending may spoil the whole effect of the essay.
The purpose of an essay un any examnunauyn is to discover how well the candidate can communicate his thoughts to other people." examiners, or markers, by means of writing Therefore essays showing great literary merit or stylistic skill are not necessary Natural and Effective statements of facts or simple presentations of arguments are quite sufficient So, you should know precisely what you want to say and to express your subject matter as clearly. pleasantly and concisely as possible.
POINTS OF CLEAR WRITING ARE AS FOLLOWS-
BE STRAIGHTFORWARD
Use short simple sentences in preference to long and complicated ones in fact, it is the mos. effective and the easiest to handle Sentences of suitable length should form the basis of any
essay
|_ But, it is important to make sure that each sentence is complete
BE SIMPLE
Do not use ornate or flowery language, but use simple constructions of sentences and try to avoid elaborate metaphors.
BE CONCISE
Try to avoid repetitions and irrelevant words and if possible, replace a phrase or two words by a single word
BE NATURAL AND BE PERSONAL
Do not try to imitate others style but be yourself