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12

日五初月五年申戊歷

WAH KIU YAT PO

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英中會考物理科答案

iv) Its maximum velocity will be

1

育教俘書 日一卅月五年八六九一零公年七十五國民中

provided tne temperature remains constant, (b) When the tube is placed horizontally

•

陸永熾 •

'mg (50 = 30)

- 28 = 20

*

Suggested Answers?

PHISICS

3.4. Certificate of Education Exam.

- 1000 x 40 200 */**

(b) To determine g by simple pendulum methoo

1 heavy boli attached by a length of light (thread is hinggas shown.

*

The volume of air trapped is measured

V1 = luni

ts

The pressure equals the atmospheric pressure outside H cm. of Hg.

When placed vertically with open end upward,

Volume of air, V2 = lz

-

uni te

Pressure, P2 (H+ h) cm. of Hg.

(where_b is the length of Hg, thread,

ECTION A

(a) Archimedes' Principle

When a body is wholly or partially immersed in a fluid it experiances an upthrust equal to the weight of the fluid displaced. (b) In accordance with Archimedes' Principl

the balloon is acted on by an upthrust equal to the difference between the weight of air, displaced. the total weight. The balloon (wt. of envelope and hydrogen) and the density of air is about 14 times that of hydrogen. The greater the difference, the larger will be the lifting power of the „ balloon.

In upper altitude, where the air deconas rars, the density of air dimishes. Thus th difference between the weight of air displaced and the total weight of the balloor approaches zero. The balloon stops rising and; suspends in air,

e) 1) The upthrust on the block

\ir water U gm.wt.

•

(800+200)gm.wt.

1000 gm.wt.

**KODRAS

1) By Archimedes' "Tinciple

upthrust- wt. of water displaced?

.*. Wt. of water dieplaced

-1000 gm, wt.

Tol. of water displaced

- 1000 c.c.

Volume of the block -

1000 C.G

* CE MOTOR IN 13.

(111) The density of the block –

12.00

80

1000

. 0.8 gm./c.e

iv) When the block is weighed in liquid I

the balance reada 50 g

Thus, the upthrust is (800=5wjgn,wha It displaces equal volume (1000 c...) of liquid. X. ·

Therefore, the density of liquid X

750

1000

0.75 g.

the pendulum length (&) is carefully

measured. The bob is given a amall displacement, released, and it begin to swing, The time far 50 complete swints (a−→→→◊ →→→→ B →→→Û—¡ as one completa vibration) is messured by a stop- watch. The period (T) of ons complete vibration is calculated. :

Since T-12 X

72

therefore.

/The cobleration-duf

Thus, determined. cautions

The pendulum length should be measured barefully:-

a) Make sure the pivoting point is sharp clamping the thread with two coins. b) The actual length should include the

radius of the bob. The vernier calipers. will measure the radius,

(2) Do not let the stand to dangle. This is done by placing a heavy weight on the base of the stand.

Make sure no draught in surrounding.

Time the period by the average of 50 complete Bwing.

:) By Newton's second

,motion ܀

where F the horizontal force

71

yo

- má

J

5 gm,wt

5 x 1000 dynes

mass of the body

- 1 kg

1000 gm.

a - acceleration of the body along the

table tog

-

222.j

,0002

- dump Imą om zo avm OQZ

F

3.

m

5000

The total upthrust (D)

-The weight of the wooden block (M)

→ the wt. of the metal lump (X)

The upthrust –

dieplaced

(1000+)

ws. of water

ter

gw.wt.

M

10

•

800 + M

1

WA

(1000 -

: 10 - 200,

9 - 2000

2000

M

4

2. {a} }'14* ham i to"maximum"potential energy" is)

at A.

.E.

ས

2 x 100°

* (130

80)

0

2 x 100 x 50 100,000 arga

11) It has its minimum potential energy is

a1 D

P.E..

07

* x 1000 x 30

- 60000 #‡gs

• 6 x 103 joules:

VAN DE VILLA ESO -

A

1000

21

5 cm/sec2

PUBLIC LIBR

"motion-equation",

where S distance moved on the

- 40 cm 3

initial velocity

0 (starts at rest) -time taken

A

t

Tapis

acceleration along the table top

25

80

44 80.

11) After 4 sec, the body is at the edge of

the table. Its velocity then

V

= u + at

= 5 x 4

* 20 ft/sdi

As it falls, it is no more accelerated horizontally. In: 0.2 sec. later, the~ horizontal distance travelled.

S = 0.2 x 20

- 4 CM.

iv) When it 'falls, it is accelerated verticalis

by - 1000 cm/sec. After 0.1 second

the vertical distanca travelled

When placed vertically with open end downwards

73.- £3

units

= (8 ~.h) cm, of Hg.

If the product of F11

יה

ils

P2V2 and P3V3 :

calculated, it is found that they are approx. constant, Boyle's Law is verified then,

(e) The tube can be place alantly and the pressure,

and volume, are taken as follow:-*

Volume 1e measured by, which is,

2 AB2 + BO2 (units)

ressure (H ± hain ́0) cm.

BC

Bin

or mercury;

(AB and BC is measured by counting the units

on the graph board).

(d). i) Volume against pressure,

MICHD<

PRESSURE

11) Volume.against

MICPBC

pressure.

1

) 1) The pressure at A 18:-,

QP..= {75 + 25)

'*100 om. of_RESOREY,Y

11) By Boyle's Law,

!

before lowering into mercury,

P-

75 cm. of Hg

V = cm length of tube) at B,

*:(75 +,25 + 15)

-115 cm. of mercury)

v - 15 om

751 - 115 x 15

- 115 x 15

75

25 cm.

iii) When the volume is halved.

111 it posseases its faximum kinetic energy

at D and is

E.E.

. P.E. AT Å --

P.E, at

40,000 STEN

K -

ut + *gt2

0 + * 1000 x 0,01

5 cm.

3. (a) Boyle's Law

The volume of a. fixed maag of gas is` inversely proportional to the

*mersUTS.

l

P X.

1

75 l

2

。

- 2 x 75

23

'C' will be 75 +

86.5 cm. deep,