(the bench or board should not be sraken or tapped) when this takes place. The face
新二第三第
日六廿月十年卡丁E豆
WAH KIU YAT PO
0968
英文中學會試題預習欄
物理科 (九)
陸永熾 ·
Physics (9)
15. Solution
Let a ft./sec. be the uniform acceleration
the bicycle acquired as it ascends the
inclination of 1 in 10, and is1 ft, be the distance travelled during that interval of
tima.
A
Potential Energy gained.
wgh ft-pd1
aan ft. lb.
200 x
208 ft
Ainetic energy loss.
• jm (v2 - u2) ft.pdl
100 (v • u) (▼ - u) ft. p.
100 x 30 x 20 x (z
100 x 600 x 882
32 x 600 x 6
ft.lo
friction, F, has reach its maximum valus on limiting value and is equal to the total weight of the pan and added weights..
Extra weights may also be put on the top of the block and limiting friction is determined,
A table such as the following is obtained:
Total wt. of
block and
Total wt of scale pan and added
added weights (h) weights (F)
The value of the coefficient of friction
are very approximately constant. The average of them is the required value.
Given: P force that
prevents
slipping
limiting
friction
AR
¿vertea work done
12100 ft.lb..
xt ft.lb.wt.
where t is the time interval and 10
work done
(average yo
20
By equation of
sin
W sin
# sin 45
120 x 0707
56.56
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有致偶華
1968
英文中學會考試題預習
化學科
王錦釗。
coef, or friction
R normal reaction.
- W co845°
wt. of the body
hemistry (9)
sietriane 15 a very stable hydrocarbon and is very
inactive. It has no action with strong, acids.
alkalis, oxidising agents, or halogens under ordinary conditions,
(T) Action with oxygen-
Methane is a combustible gas. It will burn in an excess of air to form carbon dioxide and wäter, -Carbon dioxide and water are also formed when a mixture consisting of 1 volums of methane and 2 volumes of oxygen (all volumes being measured at the same temperature. and pressure) is sparked.!
• 202 ・ 002
If methane is burnt in a limited supply of air, however, incomplete combustion results, and carbon monoxide is formed.
ZCHL 302 200
صاح الي
Methane is also oxidised commercially by the use of oxygen or steam at high temperatures to form a mixture of carbon monoxide and hydrogen, the products obtained being useu manufacture methanol and armonia.
2CH
CHL
200
By conservation of energ
Kinetic energy loss + work developed
energy gained
Potential
121:00
208
35#
12100
230
If he did work at all,
Kinetis energy loss
Potential energy gali
1.2100
الرمان
12100
3 x 20
2012 ft.
Ans. If he works at an average of
ft
will ascend 230 10 ru
tr:
LO
ONG
mom does not work at all, he will ascen
It.
(b) hork done per min. au 4*
1000 x 10 x 50 ft.lb.
500000 ft. 16.0
This equals the gain in PiE. or the water per,
what is also given K.E. of M
Volume of water discharged per min.
** v x 60 cu.ft.
1000 gallons
The force P is 56.6 lb.wt
Fuestion for next÷wACK
(a) Describe and explain orterly one useful. appl
tion with increasing temperature of 1 (1) solid; (11) liquid. Also describe briefly one case of expansion with temperature being a nuisance, and explain how the of
may be reduced or othe Two identical the with a Centigrad Fahrenheit #cale
between
expansion
barked one th a
B and Con (11) What ten
and 0 on the (iii) How far (sv) How far
20.6mm
GKONG IBI
Kinetic energy imported to water per min,
1000 x 10 x 64′′ ft.pdl
10 ft.lb.
500000 + 640000
Total energy gained per
1140000 ft.lb. 1140000
550 x 60
34 II
6
Ans. The pump works with 34 h.p.
16. (a) Coefficient of static friction is the ratio of
Tinting friction to the normal reaction between two sliding surface
Limiting force is the minimum force that
causes a body to start sliding.
Coefficient of kinetic friction as the
ratio of the friction when slip occurs at constant speed to the normal reaction between two surfaces,
To determine the coefficient of static friction
a body.
LIBRA
(e) a flask is fitted with a tube and is inverted
so that the end of the tube is under water The amount of air in the flask is adjusted that the water level comes to some convenien point in the tube. How does the arrangement work as a thermometer?
Explain why this type of thermometer 18 useles practically.
111) Substitution reactions-
In the presence of ultraviolet light or diffused sunlight, a mixtura methane and chlorine produces a mixture or substitution products,
ROL
methyl chloride) CH2C12
CH2C1• 12 • HCI
(methylene
dichloride)
•CHCL
(chloroform)".
CHULT
(Carcon
tetrachloride)
If the sumel naxtura 18 sparked or exposed tó bright sunlight, the nexture will explode foraing hydrogen chloride and carbon.
CHR
(2015:
(b) Ethylene is an unsaturated hydrocarbon, and is
rather active compound.
[I} xetion with oxygen-
Ethylene is a combustible gas. It wil burn in an excess of air to form carbon dioxide and water.
C24L 302-
2002
(2824
If there is insufficient air, some carbon will also be formed which cause the flam to become smoky and luminova.
(11) Addition Resetions-
ine outstanding chemical reactions of ethylene are addition reactions. Addition takes place across the double bond to produce. a saturated compound.
(1) Action with hydrogen
mixture of ethylene and hydrogen passed over finely-divided nickel at 120°, or over platinum black at room temperaturs will förm ethane.
(11) Action with chlorine or bromine.
Ethylens combines readily with chlorine and bromine at room temperature to form the oily liquide ethylene dichloride, CH4012, an ethylene dibromide, Coh¿Br2 respectively.
C2H4Br2
A small rectangular wooden block, rests on 4 horizontal bench, is tied to a scale-pan passes cover a freely ruming pulley, Various weights
are placed on the pan till the block lust mover.
18. (a
Define velocity ratio and mechanical advantage of a machine, and describe how they may be found by exbariment for a bullev system.
A block-and-tackle system consists of a fixed block of three pulleys and a movable block two pulleys, a string being attached to the Lower block and passing over each pulley. Th mass of the lower block is 50 lb.
when a load of 200 16, là hung sau kh lower block an effort of 60 lb. weight is required in order to raise it.
That is (1) the velocity ratio, (11) the mechanical advantage, (iii) the efficiency, of this system, and what would be the efficiency for the same value of the load in the absence of Friation?
(111) Aotion with halogen hydridea"
The halogen hydrides, especially hydrogen iodide, add on very readily to ethylene to form ethyl halides.
HI C2HI
ethyl iodide! HBr C2H5Br
ethyl bromas Action with concentrated sulphurie, 2010,
Ethylene reacts with cold concentrated sulphuric acid to form ethyl hydrogen sulphate.
H304
If this is diluted with water and athyl alcohol is formed...
C2H5OH + H2S
C2H HSO #20 Ethylene may be distinguished from methane by passing each gas through bromine water. Ethylene will decolourise bromine water, whereas mathane bas no action with bromine
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