頁二第七第 日一初月九年子甲囓夏
WAH KIU YAT PO
15-85a!
1985
中學會考試題預習專欄
from which
R=10 N
(Ans.
物理
(=)
明德出版社盧雄國 提供資料
PHYSICS (2)
H.K. LO
MILL & DALE PRESS LTD.
Suggested solutions to Exercise
one
(Take g=10 ms
1.
(a)
toog
As shown in the force
diagram above, take moment about A.
F(OH)=100g(AB).
where F is..the horizontal force required. UA3x100 m-5 »
OB=5-4×1 m
T2
AB-JOA-OB
2
√5-OB
24.in
=4.899 m
P(1)=100(10)(4.899
F-4899 m (Ans.
(ii)The minimum force
Fi should tangent
(i
to the wheel as shown in the diagram below.
4-m
100g
Fmir
s Langeni to the wheel at point C which is
one of the
extremes of diameter AOC of the circular Wheel
Taking moment about
A
Fmin(AC)=100 (AB)
min
-489.9 N
(Ans.)
If the force is applied to the 10 kg block..
long skg jokg
where
is the force 1 between the blocks the reaction of 5 kg block on 10 kg block
Let the acceleration
of the system be a
2
F-R10a
F=5
(2)
also, F=15N solving R, from (1) and (2)
we have -
=SN(ATS.)
(ii)Similarly, let the
force between the
blocks be
be la
and the
acceleration of the
system be a
ms
M
Take the upward
direction as positive. Let the tension in the spring of the spring balance be 1, the acceleration of the elevator be a and the "mass of the block be
m
weight of the block
ng
.T-DA
(a) when a 2.5 s
報日僑華
the smooth wall. R the resultant
force acting on the lower end of the ladder. -the vertical,
component of R. f the horizontal
component of R. frictional force between the ladder and the floor.
W=weight of the
ladder.
(if)Since the ladder is in equilibrium,
T=100 N
Substitute into
m#8 kg
True weight of the block 50 N. (Ans.)
An's
(b) T=54 N
Substitute into (1) 64-8(10)=8a
a=-2 ps
(Ans.)
Ans: The elevator moves
downwards with
acceleration 2ms (Or the elevator has an upward
deceleration 2ms-2)
(c) If the elevator moves
upwards with uniform speed, then a=0 From (1)
T=ng+0
T-ng
=80 N
(Ans.)
Hence, the reading of the balance is 80 N.
(d) If the elevator moves
downwards with
"uniform" speed, Trence we have also a=0
T-80 N.
(Ans.)
Therefore the reading of the spring balance is 80 N.
(e) If the cable wire
breaks, then the elevator will fall down with acceler- ation equal to the gravitational acceleration g.
Heuce
T-ng-ng
T=0 Therefore, the read- ing of the spring. balance will then be: ON.
(i) The force diagram
shown below:
where
A
Normal
reac
acting on the
upper end from
therefore,
No-W-0.
(2).
Taking moment about
B
1x3−N,x8=0·
5W-8N1
From (3)
3x160(10)
8
N
=600 N
(Ans.)
The direction of the force acting on the upper end of the ladder is perpendicular to the vertical wal with magnitude 600N. (iii)The frictional force.
fis From (1)
tal.
(Ans.)
(iv)The resultant R
- √ E2+N2 -√6002+16002
-1708.8 N
(Ans.)
Also,
tang=
6=20°33'
(Ans.)
Ans: The resultant at
the end of the Tadder is 1708.EN making 20 55' with the vertical.
Let v
be the and v
velocities of the block A after the
bullet emerges and
the buliet as it
emerges from block respectively,
By conservation of energy
2
\(2)v.2=(2)(e)(0.2)
2 ms (Ans.)
(11)By conservation of
linear momentum The
initial momentum
(0.01)(2400)
-24 kgms
1
The final momentum
=(2) ▼ +(0.01) (VD =(2)(2)+0,010,
=4+0.01v
-24-4+0.01v,
1
−2400 ma1 (Ans.)
(b) Let v be the velocity
of the block B and
the bullet after the bullet hit the block B.
Since the bullet is embedded in block B,
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hence, by conserva- tion of momentum
(0.01)(2000)-(0.01
By conservation of energy
4(0.01+0.99)(20)2 =(0,01+0.99) għ
h÷20 m
(Abs.).
As shown in the force diagram below
W
The bouyant force B will apply at the mid-point of the part of the rod submerged in water. (ii)W-Weight of the rod
-1.2 12N
w-weight at the end
of the rod to be determined.
The volume of the rod
1.2
*0.5xd
(where d is the density of water)
Volume of rod
submerged in water
2.4
CA M
3-
The bouyant force B
weight of water displaced by the rod.
-(density of water)
x(volume of the rod submerged)xg
=dx=x10
=20 N
(iii)Taking moment
(Ans.)
about
(Bsine)(2.5)
the hinge
=(k'sino) (3) + (wsing)
+(wsine)(6)
2.5x20=12x3+62:
w=2.333 N
生物
BEL
BIOLOGY (2).
W.W. LEUNG
(Ans.)
日五廿月九年四八九一番公年三十七厨民華中 育教僑華
-an ail emulsion
11. add juice Y and
shake. The appearance after standing for. 1 hour ist
-oil layer
Add juice X+juice Y and shake. The appearance after standing for is:
1 hour
-an oil emulsion.
Name X and Y, and state the digestive glands by which they are produced. With reference to Experiment 1, state. the function of X and explain the importancé of this function to digestion
c) Describe and explɛin
the results of Experiment II.
d) Describe and explain
the effect of X on the action of Y. 4. The diagram below
shows the vertical section of a resti
Gam
Jaw-bone
Name two elements in the diet which are essential for the formation of substance
X.
b) State two types of structure found in What are their
functions?
EZBE★#c)
MILL & DALE PRESS ITD.
Unit 1: Nutrition
3. X and Y are the
digestive juices of man. The diagrams below show their actions on oil and boiled egg-whith
-oil layer
water
-boiled egg-white
and juice and take;'
The appearance after standing for 1 hour
is:
雙程 探親
* *#*# 可往外國
Food sticked at position Z may lead to the development of cavities. Why?
d) Which chemical is
being added to our drinking water to reduce the incidence of tooth decay?
e) Name two vitamins
which are important to our healthy teeth.
5. The following diagram shows the internal structure of part of the wall of the mammalian sma11
intestine,
JA
a) ame the structures
X, Y and Z..
b) (1)ow is maltose
digested in the small intestine. (2)How is the
product of this digestion absorbed at structure X2 (5)Through which blood
vessel is this product transported from the intestine? (4)here and in what
form is the product stored?
(1)What kind of food-
substance is. transported by structure 2? (2)Name two locations
of the body, where this food substance is stored.
a) Xbile; by liver.
Y gastric juice; by
gastric glands.
b) X acts an emulsifying
agent that breaks down the oil into numerous small oil droplets. This
greatly increases, the surface area of oil and therefore facilitate the
digestion process.
The boil egg-white has been partly digested, Pepsin in Y carries out the digestion.
d) X contains sodium bicarbonate which
creats an unfavourable alkaline condition for the proper functioning of pepsin.
a) Calcium and
phosphorus,
b) (1)Blood vessels:
supply nutrients for the growth of: the tooth. (2)Nerve fibres: to
give sensation. Bacteria way act on the food and produce acids. The acids have a corrosive action on the enamel and then the dentine.
d) Fluoride.
51
Vitamin C and vitamin
D.
a) X=villus
Y-blood capillary Z=lacteal
b) (1)The maltose is
digested to glucose by the enzyme maltase in the
small intestine. (2)The product glucose diffuses through the epithelium of: the villus into the blood capillary. 5)Hepatic portal
vein.
(4)Glucose is stored
as glycogen in the liver and muscle.
(1)Fatty acid and.
glycerol.
(2)Underneath the skin
and around the kidney.
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