1970-02-12 — Page 14

第二張四第七月正ㄣ戌庚夏 WAH KIU YAT PO

郭日僑華

四期星日二十月二年〇七九一年九十五國民中育致潘

1770英文中學會考試題預習專欄

堅道英文書院主編

物理科

(十五)

PHYSICS (15)]

Bolution for Exercise 14

Solution

By the Lee of Floatation, a rioating. body dis-places its own weight of liquid. That is, the product of the volume immersed and the density of the liquid is constant for a given hydrometer,

When immersed in water, the volume immersed di The volume of the bulb plus the voluma

• of 2 cm of stem

5 • 127 × 0.252) c.c.

When the hydrometer is placed in a liquid of nepific gravity 0.95 the volume immersed is

+ (lπ x 0.252)

(where is the length of stem immersed,

since the hydrometer displaces its own weight of Aiquid,

5,+*(27°C × 0,25′′) = 0.95(5 +£π x 0.25* 0.062570 (0.95(-2)= 5(1 −

0.95)

10.95%-2-0.06236

0.95 0.2572

0.5 TC

0.95 x 0.25

3.45

The hydronster will sink to a depth of. 3.45 on 'above the bulb in the liquid o upsoifio gravity of 0.95..

Owing to the buoyance or upthrust of air Maighte in air of the cork and the brand aro Losa than they would be in a vacuum.

Archskedés* Principle, the loss in we weighs in aqual to the weight or air displaced

45.75 Volume of brass

1845.

Answer

0.3 cm

16

174

16 x 70

17. x.13.6

4.8 cm

The changes in level onthe two limba are 4.8 and 0.3 om respectively,

and 2

be the part of the sphere oil and mercury respectively. The volume of the ball-

- 10

Jpthrust of oil

Upthrust of mercury

As the sphere is floating in equilibrium condition,

+ 13.672

- 10 1.8.9

89

Solving equations (1) and (11)

1 10 x 13.6 - 8:3

-1024-7

10 x

10 x 8

12.7.

6.3.0.0.

(11)

fsavery" "367 end 6.3 0.0, of the sphere are in oil and

mercury respectively.

REVISION ON MECHANICS IN THE FORM OF MULTIPLE CHOICE"

WEST

volume of air dispoaced by brasa

Direction

Height of air displaced by brass

Weight or brass in air

Nelume, or cork (approx.

45:75

x 0.00129) gu.wt ➡ loss in weight of brass:

x: 0.00129.

45.75 - (45-75 45-75(1 - 2.00122) gm.ws

weight of gork in sir 45.75/0.25

0.00

volume of air displaced by

Dork

Weight of air displaced by the cork

Turke, walźht of co

(45.25

x 0.00129) gm.

lode in weight of cork. weight of cork in vacuum weight in air + lose in vt.

-[45.75(1-000129)]

0.2

x 0.00129)

0.00122 0/00129

45,75.(1 - 8.5

Answers and explanation" will be given

in the next ishue)-

saca question or incomplete statement below is followed by five suggested answers or choices. Select the one that best answers the question - or homplete: the statement,

At a given place, two substances having the game mass have the same (4) Volume

density.

specific gravity

helative density

or a space wahtele on the earîn 18:0 heavier than that on the moon. If the vehic moves at the same speed on both the sirth and the moon, the kinetio energy it possesses on the moon will be

(A)" b ́times greater

6 times less

36 times greater

36 times less:

the same as on the cazz

HOW BAould we place the prism on the table in order to have the minimum pressure on the

10.

15.

Two solid spheres, A and B, of identical radii, are

placed in a beaker of water. The sphere â hág a

specific gravity of 0.5 and that of B is 1.5. It ie found that

(A) A floats and B sinks

(B): both sink

(c) both float with the Banʊ volume above the-

water surface

(D)

both float but à floats with a greater port- ion, above the water surface.

() both float but B floats with a greater port-

tion above the water surface

Some water is poured on a desk and a piece of plane glass is placed on it. It will require a consider- able force to lift the glass from the desk. Thie is because of

the cohesive force

the adhesive force

the surface tension

the viscosity of the liquid

the weight of the glass.

An iron ball and a tennis ball are dropped at the same time and from the same height; neglecting air resistance

(1) the iron ball reaches the ground first

because it weighs more

C)

(D)

the tennis ball reaches the ground first because it is lighter and travels faster

the iron ball reaches the ground first as

it has a guzller volume

the tennis ball reaches the ground first sa it is hollows

(1) they both reach the grond at the same tips

despite their masses

A boy throw a stone vertically downwards from a tower, 2500 in height with an initial speed of 20 It/sec. After second the stone had a speed, in

(A)

(B) 16

(c) 30

(D) 32

(B) 36.

As a Dus Accelerates uniformly, therɔ ia no chan in its

inertia

velocity

kinetic energy momentum power

A car starting from rest, tzavēle a distnace of 5. fest in the first second. If it accelerates uniformly at this rate for five seconds, it will travel a distance of

(4)

25 fest

(B)

75 feet

100 feet

125 feet

(E)

625 feet

Raising a 550-1b body through a vertical height of 4 feet in 2 Bec requires a power of (in horsepower)

(D) 8

The return of a ball which has been thrown into the air depends on

the specific gravity of the ball

D).

(0)

D)

the force with which the ball was throw gravity v AL

the air pressure.

E) the size of the ball

The smallest resultant of two

6 poundals and 8 poundels 10

2 pdl.

6 pd1.

(0);

8 pdl

nourrent föreds of

45.75 (1+0.00511

45.98 gm.ut.

Sanvezi”. The true mass of the work 18 45.98

D) 10 pdl.

E)

14 pdl.

If three or more roress act on a body, a state of quilibrium is acquired when i

the resultant foros in any one direction

1010

the resultant force acting on the body, le

A11

II.

[II.

the algealu sum of the moments on the foross about any point is zero

3.7

/ Let h, and R2 be the displacement in liquid lavals of the önállex and larger lisbs respec-

from the diagran

Being on the game laval AB, the pressures on the liquid surface of both limbs are qual.

xd

where d is the density of

лексику

The volume of mercury depressed by water column should equal to the volume of mercury pushed up on the other limb. If A, and A, be the area of the two limbe, 42 m 1642

It should be placed with

the side ABCD on the tapia

the triangular area 4BF on the tab.

1" x 3" Bide on the table

1" x 4" side on the table

It is independent of the area.

The hydraullo press Works on the principle that

the liquid is enclosed in the machineory. the liquid transmits pressure equally in all directions.

the liquid has henalty

one piston is larger than the other

a small effort overcomes a heavy load

Two BUDE Tances or specific gravity 4 and 5 respec tively are mixed in the ratio of 2 to 3 by volume. That is the specific gravity of the mixture?

A) 1.8

(B) 4

IV. the lines of action of the forces, when promi

duced, are concurrent

Statements Correct

I, II and III only

B

II and III only

(C)

I and III only

(D)

II, III and IV on:

other combinations

The centre of gravity of a body

must be within the body

may be near but not necessarily within the body

changes its position from time to time will be raised when the body is slightly t tilted

18 he resultant weignu ox Biz particles com posing the body

The ping-pong ball inside the bowl is

Solving equatione

162 and (11),

(11).

17d

70

-17 x 13.6

(0) 2.6

(D) 8.4

10.0

Two suge vances that apparently lose the same weight"

when immersed in water must have the same

(A). Volume

(B)

denëity

(D) weight in sir

weight in wat?

not in equilibrium in stable equilibrium in unstable equilibriu. (D) in neutral equilibrium in rolling equilibrium