育新倭華 百三節張六第 日七初月二十年德已圈系
WAH KI YAT PO
報日僑
三期星
日四小月一年〇九一年九十五國民难中
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13. (B) is correct.
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the block, the force acting upward
on the object is (F-
When the effort is F, and isolating
W)
F
考試題預習專欄
英文科
(十一)
王淑方,
The acceleration is then,
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(F-W)
LESSON ELEVEN
14-1-70
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70英文中學會考試題預習專欄|
堅道英文書院主編
物理科
Physics (11)
(+-)
Answer and Explanation to the Multiple Choice Questions of the last issue.
EXPLANATION (for the difficult ones only)
1. (D) is correct.
Pay attention to the fact that the weight of the metre acts through the 50-em mark.
2. (C) is correct.
The slope of the curve indicates the speed.
Only graphs B and C have a variable slope along the curves which show that the spaad is changing.
The slope of C decreases as time goes by, This means that the moving body decrease in speed.
3. (D) is correct.
The distance covered is measured by the area under the graph.
At the specified time IV, the moving object A travels
(6 +2)
x 6 24 ft.
The distance moved by object B is
4 x 6 - 24 ft.
4. (C) is correct.
Applying the equation of motion
- a
2
- 2a9
where S is the height
- -g negative due to the upward flight,
g is the acceleration due to gravity
v is the final velocity which in zero
u is the initial velocity, 16 ft/sec2
5. (c) is correot
00 is the diagonal of the parallelogram OABG. Forces concurrent at 0.
6. (B) is correot.
Top of swing.
Bottom of Bwing
E + K
Ep + Ex
0 +
Amy2
mgh + 0
Therefore,
7. (E) is correct.
zgh 8 ft/s00
Momentum is the product of mass and velocity.
8. (B) is correct.
Definition of force. Į
9. (C) is correct.
When the lift is stationary or moving with constant velocity, a push exerted on the floor is exactly equal to the weight of the person.
If the lift is accelerating upward, another zorce, P-ma, is taken into consideration. The total force exerted will be
W + ma > W
10. (B) is correct.
Ex
kinetic energy
Fa
II
+
11. (E) is correct
Ek (mv)2
Force causing the system to move
Kass of the combination
Acceleration of the system
- 16 lb.
12. (A) is correct.
י
- 4 x 32 pdl'
* 12 + 4
I
(4 = 32)/16
-
8 ft/sec/sea
Assuming that the arrangement is an ideal one, efficiency equale to 100%.
Velocity Ratio of the inclined plane - Совес * Velocity Ratio of the cylinder - V.R. of a movabla
Velocity of the combination
Since the efficiency is 100%,
pulley - 2
- 2 CODEO
Mechanical Advantage of the combination
V.R. of the combination
Load (W)
Effort (E) Effort (B)
-2 0040 0
W
2 Bin 30°
Bin 30°,
- *.
M
where M is the mass of the object.
When the effort increases to 2F.
the force acting upward on the object is (2F - W).
The acceleration is vAS
(2FW)
at *
М
2(F
(2F W)
therefore a'
a1
W);
2a and also
14. (A) is correct!-
W
2 F
All the statements except IV are correct. The maximum force of friction (limiting fricting) is equal to the waight (normal foros) of the block times the coefficient of friction. If the applied foros is less than the maximum force of friction, ta block will remain at rest.
If the applied force is greater than the maximum friction, it will accelerate;
If the applied force is equal to the maximum friction, and is given an initial push, than aooording to Newton's first law of motion it will continue to move with a constant velocity.
The block cannot accelerats in a direction other than that of that of the applied force.
15. (B) is correct.
By the Principle of Conservation of Momentum, Total momenta before collision - 14 x 10+ 0
140 ton-mph
(10+30)v ton-mpa Total mamanta arter coll1810n Total momenta before collision - Total momenta
after collision 140 - 40v
v3.5 mpa
16. (B) is correct.
Prese ure of kd
cc a
The heights are exactly aquali The pressure are the game.
17. (B) is correct.
The large piston risse 2 inches.The volume on this Bide of the press incresses 27R".
The smaller piston has to press dom.
27 R
2 x 15
"
1
+
In each stroke ind
mali
4 passen MOYEN
ANUZO2 +
Total number of strokes needed is 32/4/'- 8
18. (B) is correct.
The liquid levels on both limbs are equal, but w heights of liquid columns are unequal.
-
E
1
16/20 - 0.8
19. (B) is correct.
The depthe given servas merely as distreators. The ball displaces 80/0.8 100 o... of water. It, therefore, experiences an upthrust of 100 gm. wt. which exceeds the weight of the ball by (100 - 80) gm.wt.
The reading of the spring-balance is 20 g.wt.
zo (D) is correct.
Kinetic energy of an object depends only on its mass and speed.
Direction of motion is not a factor.
21. (E) is correct.
The period T of a simple pendulum is inversely proportional to the square root of g. Tie least when is the gresteet. At the two poles, where the globe flattens there, g is greatest,
22. (B) is correct.
Use the equation of motion: S - ut +
Fat2
where S is the height of thể
cliff
2
therefore
576/16
+ - 6
23. (D) is correct.
u is the initial velocity
which is mero
t is the time takan ag (acoeleration of gravity)
Mass of a body is ite quantity of inertia..
24. (B) is correct.
Newton's Second Law of Motion states thất P - na - Mass of the body is inversely proportional to the acceleration.
25. (B) is correct.
Specific Gravity of the stone
Wt. of stone in air
Wt. of equal volume of water
Wt. of stone in air
CHAPTER TWO
GENERAL ENGLISH
(D) THE ARTICLES (Continued
THE USE OF THE DEFINITE ARTICLE 'THEL
The Definite Article is used:
e.g.
(a) When we speak of a particular person or thing. The book you lent me was lost. The man you met yesterday was my uncle. (b) When a singular noun is meant to represent a
whole class.
e.2.
The dog is a faithful animal.
The rose is the sweetest of all flowers. NOTE The nouns. 'man' and 'woman' used in the general sense to denote the whole class never take any article.
e.g.
Man is the cleverest of all animals.
(c) With names of gulfs, rivers, occans, seas, groupi
of islands, and mountain-ranges:
e.g.
The Persian Gulf, The Indian Ocean,
The British Isles,
The Red Sea,
The Canges,
The Himalayas,
(d) Before the name of a country that is a union of
smaller entities.
The United States of America, The United Kingdom,
e.g.
The U.S.S.R.
(e) Before common nouns which are names of things
unique of their kind.
e.g. The sun, the sea, the earth, the sky. (f) Before Proper Nouns only when they are qualified
by an adjective or a defining adjective clause.
The great Caesar, e.g. The
the immortal Shakespeare
e.g.
(g) Before the names of ships, trains and aeroplanës,
The Blue, Train, the Flying Scotsman. (h) Before the names of hotels, shops, institutions, etc., where the name is an impersonal one.
The Ritz Hotel, the Chartered Bank
(i) Before the names of musical instruments used in a)
general sense.
e.g.
Jane plays the piano everday. Jack learned the violin three years ago,
') Before Superlatives.
*.g.
This is the best book in the library. He is the brightest boy in the school. (k) Before adjectives used as nouns denoting a whole
class,
e.g.
the rich ( rich people) the poor (= poor people)
(1) Before a common noun followed by a proper noun
which identifies it.
e.g. the planet Mercury,
(m) Before ordinals in titles.
e.g. King George IV
the play 'King Lear'
(King George the Fourth)
THE DEFINITE ARTICLE SHOULD BE OMITTED:
(*) Before an abstract noun which is used in a
general sense.
e.g.
NOTE:
Life is hard for some people.
We use 'the' before abstract noune that are limited or qualified. 9.g. The life I live here is hara.
(b) Before names of materials.
e.g. Rice is grown in China.
Silver is a useful metal.
(c) Before plural nouns used in a general sense.
e.g. Magazines are my best friends.
(d) Before names of meals used in a general sense,
Will you come to dinner (tea, lunch' with me?
e.g.
(e) Before most proper nouns.
e.g.
Kelly went to France last month. Joan lived in Main Street.
(f) fore Lake, Cape, Mount.
e.g. Lake Erie, Mount Everest,
NOTE: When the words Lake, Cape, Mount are
followed by the preposition 'of', 'the' is used.
e.g.. the Cape of Good Hope.
(g) Before titles followed by a proper noun.
કફન
e.g. King George,
With names of languages,
e.g. He speaks Cantonese.
President Lincoln,
(i) With words that the idea expressed concerns the
use made of the building,
These words are:
school, prison, hospital, church, etc.
e.g. My brother goes to school (to learn)
everyday.
He goes to church (to worship) every
Sunday.
NOTE: If we add the definite article 'the' before
the words school, prison, church,
e.g.
etc., they will have a different meaning. My brother goes to the school (just to see
the place).
He goes to the church every Sunday (merely
looking round).
Before names of seasons and festivals,
Spring is the best season of the year. We have not school on Christmas Day. (k) Sometimes before predicative superlatives.
(3)
Apparent loss, in wt. of stone in water
125
125
75
- 2.5
e.g.
Your advice was most valuable. She is happiest when she is reading her books.
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