1969-02-19 — Page 15

REFER

RARY

21 FEB 69

育教僑華經馬儒華質三第張四第日元初月正再商讯魔更WAH KIU YAT PO報日僑

三期星日九十月二年九六九一圈公年八十五國民華中

1969

「CC 文中學會考試題預習

物理科 (十六) 陸永熾:

-solution

PHYSICS)(16)

Mechanical equivalent of heat is defined as the

mechanical energy required to produce one unit

heat, that, is, the number of units of work

required to produce one unit of heat..

It is expressed in "ergs per caloris"

"ft-lb. per B.Th.U:"

(b) Determination of J, Machanical equivalent of

Heat, by the shot-tube method,

A cardboard tube about a metraj long contains a gm. of lead shot and is fitted with corks at both ends. One of the cork has a small hole plugged with a "peg. This allows the insertion of thermometer to take the temperature of lead shot.

If the tube is inverted u

the lead shots fall through distance of hem. In so doing ngh of potential energy i

converted into heat

With the following measuremente

mad #:

inss of lead 'shot'

mgm. (not to be weighad)!

Specific heat of lead

S

height of shot falling - h am.

Initial temp. of the expt

Final temp. of the expt.

No. of times the tube is revé Then,

Heat produced - maitz Work done

ing?

mrigh

mgan

cal

EOM and A MAR are similar

210

10 130

x 135

༥

He can see a field of view behind him through 130 cm. of the width of the roar wind ch

\(h) Convex mirrors are widely used as car-driving

mirrors since they render a wide field of view and an erect image. The accompanied diagrams show why

convex, mirror has a wide field of view than a plane mirror of the same size,

PLANE MIRROR

Ang. In this case the image is 24 in. in front-

the mirror and is therefore res. 2 in. high.

This problem can be solved by means of an accurata graphical construction. Student« have to endure a practice of choosing suitable scale for both x- and y-axis,

(d) Using the mirror formula

ira u • object distance

focal length image distance

CONVER WIRROR

.75 cm.

ghn/1075(t-t1) joules/caloria)

m is eliminated finally, therefore, it should] not have to be,"

(c) For a mass, M lb., of water falling down from a height of 150 ft, potential energy lost

mgh

150 mg ft-l

* 150 m ft-lb..

150.m

150 a Th. U

Heat gained by water

*15'

78

0.192 F

Ans. The difference in temperature at the top

end bottom of the Fall 19 0.192°F.

In retarding from a spand of 800 m/s to 100 m/s, the meteor has its EiE, loss of AKE developed

into heat.

The K.M. loss. AK.E. -[4x10x8002-4x10x1002)

Joules 1x 10(64−1)

23 x 205

752 kcal.

Ans. Heat developed as it retards 752 kcal.

30.(a) let M be the mirror of 10 cm. width.

be the mid-point of it.

Marrow Hidd

wide fiel of view

By applying the mir

whare u - object distance e 6 en.

focal length - 8 cm image distance.

Image Size ubject size

[MO 5 cm.

E is the position of the driver EO 45 cm.

Width of the rear window, RR - (10) + 2x). and is MA - 135 cm. from the mirror.

in (ignore the minus sien)

Aas. The image is 24 in, behind the mirror and

la therefore virtual; and is 4 in, high; Secom case, when u - 12 cm..

cm. (ignore) the-va aign):

Ana.] The "inage is therefore 3. cm behindthe is

virtual,

Quastions" fgn next week

31.1(a) State the laws of refraction.

Define refractive index, and describe an experiment to determine its value for glass. (b) Construct a ray diagram to show the refracted

ray when light meets water surface at an angle, of incidence of 40°. (Refractive index of Water-

4/3)

to) A fly, looking down vertically into a pond from

12 in. above the surface, sees a fish apparently 18 in, below the surface. What is). the actual depth of the fish? What is the apparent height of the fly as seen by the fish? td) A tank whose bottom is a mirror is filled with

water to a depth of 20 cm. A small object hangs motionless 8 cm, under the surface or the water. What is the apparent depth of åts. image when viewed at normal incidence?

(a) What is meant by (3) total internal reflection)

(11) critical angle.

Explain, with the aid of a diagram, how a suitable glass prism may be used to turn ray of light through 180°

Light is incident on the face AB of a 60° glass priam ABC, is totally reflected at the face BC, and passes out through the face AC. What Is the largest possible value of the angle of emergence? (Take of glass as 1.5) Tel Given that the refractive index for air-glass

is 1.60 and for air-water is 1.33, calculate the critical angle for water-glass.. (d) An aquilateral glass prism is placed with one

of its rectangular faces horisontal and in contact with a dot which is in the centre of the face. Viewed from vertically above, two dots can be seen, Drax à ray diarran to

explain this.

步領

如寶

A

【戦論後賽!

INDE

運成

功

被前两乘「顉寶興「小飛俠」四位在中庸。又二乘牡爲「鶯飛廛」 ASK PERFEKA-TRUSTEE

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「快活人」在乎內之提現而訥-次然而某數接近大熱門 活人」真游定柱貴一萬五千餘谌拿骐次煞,以游定柱及 人隔之將險與潛力狖肝,大熱而熱流,然後合理。「快 無」「心」、「小飛俠」、「快活人」六啊。樣

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步如飛戦畧運用偏差

近

而飛對七一快捷五玉,變

退休練馬師

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一天

EX

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全羽 8

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