頁四第張六第日六廿月三年戌壬歷夏
WAH KIU YAT PO
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日九十月四年二八九一肠公年一十七國民華中 吉教儒嘩
5
(Aus.):
the force on
1982
中學會考試題預習專權
=-9/11 2
-45 N
(ii)
The upthrust of
=1,25×10*
(ans.
8. In the figure, a:bic- 15. The 2n term of the
th
water on the cube
G.P
8,-
(Ans.)
the weight of water
is
(The negative sign
displaced:
(#A)
indicates the force.
(1000)(10)(10) "
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100000 N
(Ans.)
物理 (廿八)
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TITYSICS (28)
|H, K. EG
MILL & DALE PRESS LTD,
Suggested solutions to
Revision Test.
SECTION AF MECHANICS, AND. "PROPERTIES OF
MATTER
(a) Since the strings are
long, inextensible. and, of negligible
therefore there
are two simple pendulums. The pendulums have the same length, there- fore, they have the same period. As the spheres are released ut the same time, the time taken for the sphere to cach their lovest position are the same and are each equal to one quarter
of the period, Therefore the sphere's will have a head-on collision at their lowest positions
[(1) Let the velociries
of A and B before collision be v4 and vo respectively.
Ry conservation of energy
mel
z (2) (v, )2
«(2)(10)(0.45)
on A is to the left) Energy Jost
-4 ( 2 ) ( 3 )2 + 3 ( 1 ) (5)2
-((2)()+4(1)(4)2)
10.25 J
(ans.)
The energy lost in this impact will be! dissipated in the form of heat, and sound,
(a) Jet the reactions
F and 6. be R. and Ho respectively. As
shown, the force: ti i 29 gettata Över bag
H=mess of the man;
75kg
Menuss of the ptanck
Since Tue, pranck is in equilibrium, the resultant of forces acting on the planek is zeno.
R
750-500-0
Rj +R=1250
Also, the sum of moment about any point must be zero.
Take monuut about p; R1 (6)~mg(5)~Mg(3)=0 1,(6)–(75)(10)(5)
-(50) (10)(5) - P=875 N.
(AUS)
From (1).
R1 = 1250¬B2
- 1250-875
*(1)(10)(1.25)
1s;
Ans)
(ii), Let the velocities.
of a and B after collision be vy and vy-respectively. Since the maximum height reached by B after collision is 0,8 m, therefore
3(1)(
m's
10)(0.8)
(âns.)
Take the tiréetion towards the "right positive.
Initial momentum
- = ( 2 ) ( 3 ) + ( 1 ) (-5) |_
1 kgms
-1
Final momentum
=(2)(v_)+(1)(4)
By conservation linear momentum
-1.5 s
(ang. )
Let the maximum: height reached by after collision bel.
By copservation of
oner.
3(2)({})^=(2)(107(1)
9/40 10.225 m
(iv) The average force
ona during the collision is the rate
of change of momentum of A.
Change in momentum =(9)(-5/2)-(216)
(Ans.
fans.)
= 375 N. (b) Suppose the planck will tilt when the man is x meters from Bä Hence, the. reaction at: P
Take coment about
Mg(3)→ng((B=xY=0 (50)(19)(3)-
~ (75)(10)(3-x }={}
fans.):
When the man ia
from B, the planck wifi tilt/
(a) The Tactors that
affect the efficiency of a single string pulley system are: Priction:
the efficiency lowers when friction increases.
2. Vejght. of pulley, and
string;
the efficiency Lowers vlen the
weight of pulleys and string increase.
5. The efficiency lovers
if the portions of
the string are not vertical
(1) The required
velocity ratio
不隨禮柯多新彩無報請遠 另報拜式采穎色任販就道 收 附出印多雜華 歡訂近閱 費送版刷姿誌僑迎閱向戶
1.4 ms Wile
Let the pulling, force: exerted by the string on the cube be T.
Since V.R,=5
MIA.
iffor
T
5x10
-805
There
Exto
Ext95
Let the acceleration of the cube be Capply:
2nd Paw.
where memass of the
cube
(2,5×1000}(10)
(2x103⁄4+10”)
~(~.3x10-)(10)
(2.5x10 )a
(Ans...)
cube wil finally stay at the Wat Surface vi tinh part of its volume immersed.
Let the volume of the ebe immersed in water be V*,” hence
Where B is the upthrust exerted, the cube.
Hm 1
=(2.5x10′ ) (10)
20x10 0.5x105 y
But B1-(1000}{g} {V®)
(1000){z}{V*)
0.5x10
Therefore, the cube. finally stay at the water Farface with half of it's volume immersed.
(v) In order to push the
whole cube out of Water, the pulling
force exerted on the block nust at least equal to the weight. of the block in air.
Wences forceTM
ne
pulling.
N
5x101 the effort
quired be E'
M.A. Again,
6.5x10
E
P=0.75x10t
80%
the additional
MATHEMATICS (Syll.2) (28)
C. P. Man.
MILL & DALE PRESS LTD.
Exercise 12
Multiple choice questions
1. If
D.
E.
√32:1
A. 3:2:1
then
108109
C. 3:2:1
D 2.5:1
Solve the inequality
(4x+3)(3x+2) >
E. X
If the bearing of P from Q is $60°W, then the bearing of Q from Pis
A. N60°E
B. NGO W
C. S60
D. S60 E
E. N30 E
5. If the length of
rectangle is increased by 10% and the width decreased by 10%, which of the following is true?
Its area remalas the sameg
B. Its area is
decreased by 1% C. Its area is
increased by 1% Its area is decreased by 10% E.Ita area is
increased by 10%
COSU=X
and _8290o, then tand-
7. In the figure, ABCD is
a square and ABE is an equilateral triangle. LCDE=
12
force required. =0.25x10"-5x10"
C. 16°
D. 30
E none of the above
2
LLLLL
E. 4:2:1
9. What is the area, în
of an equilateral triangle of side x m?
13.2
The perimeter of a sector is 16 and its angle is 2. radians. What is the area of
the sector?
A 16
E. √3x2
10.
sine+1
tane
cos-0 2tane
13.
B. 32
C. 64
D. 167
E. 327
17. If a and b are real
numbers, what is the minimum value of the expression (2a-b)'
in 0
ino
the figure
can not be determined
18. x, y and z are three consecutive positive integers. Which of the following is true?
A. x+y+z must be odd
X+J+Z must be even xyz must be odd xyz must be even
+2 Bust be
140°
200
C. 2200
D. 260°
E. 300
If the value
2
+3y+7 is 2. What
is the value
-2y-by+]
A. -13
1.7
D. 13
E. 16
of
In the figure, ABCD is a rectangle.
BEF=90, which 2 of the triangles (1), (2), (3) and (4) must be similar?
even
19. In the figure, 0-
the centre of the circle and its radius is г. XX touclie.s the circle at P. Find the distance of Q from XY.
Ar(1-sine
B. r(148ine C. r(1-c080
D. r(1+cose
E. r(1+tang
20. In the figure, EB and
EC are the bisector of ZABC and ACD respectively. If
BAC-50 ZBEC
(2) and (3)
‚Â. 40°. B. 300
B. (1) and (2)
C. (1) and (3)
8
D (2) and 4) E.
*(5) and
SP amounts te $Q in
In years at simple
interest. The rate per annum is
100n(0–P)g
P.
100(Q-P)%
n
E cannot be
determined.
Answer:
1 E
6.D
11.C
16
2 A
7 ·B
12 D 17 C.
3. E
8.D
13 C 18 D
100(0-P
· A
9. A
14 G 19 C
DP
100(
9 (9 ~P) q
5 B
10 C 15 E
20 C
nQ
1000
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