1971-05-07 — Page 22

頁二第張六第二日三十月四年亥辛曆夏 WAH KIU YAT PO

英文中學會考試題預習專欄

報日僑華

五期星

(廿八)

物理科

PHYSICS

LESSON TWENTY EIGHT

Answers To Revision Test 2

Conventional Section:

A uniform acceleration of 200 ft/seg/min means uniform change of velocity of 200 ft/sce in fin 200 ft/sec/min=200 ft/sec

Since 60 m.p.h -88. ft/sco

200ft/sec.

200×60

188

88

ft/sec

60

(1).

(2:1)

-x00) ml

28181,8 ml/br.

The acceleration due to gravity is detârmined ov simple pendulum using the equation 1-27√

there Teperiod of the swing

I=length of the string..

The experiment is done by the Tauowing steps.

The length of the string is measured.

The pendulunasallowed to suing by pushing the pendu lum slightly to one side and then let go. (N.B. the amplitude of oscillations should be small).

(iii) (be time for 30 oscillations is taken and hence fine

the perica.

(iv) During the swing of the pendulum, make sure that

swings smoothly with no torsional motion.

The above process.us repeated for different dengths when measuring the length of the string, the measure- ment is from the point of suspension to the centre. of the bob"

The results are tabulated as follows:

Time for

30.

oscillations

sec

Since the S.G. of wood is less that that

of the liquid, the upthrust F on the wood.

greater than the weight of the

By Neurony 2nin law.

of, displaced, laquid (by Archimedes Principle)

1.2)g wher

OC) 1.2

ma

volume of wood.

g is calculated by using

The velocities at the end by •v=u+gt"

and tabulated as follows:

second

32

ft./sec.

-128 160

distance covered in third second: Area under 'AB.

96).

日七月五年一七九一屣公年十六國民華中 育僑華

(d) By principle of, work

Work done by effort ework done by load e york done

the movable parts of pulley * work done to ovėj fniction.

Let the distance moved by load be. I uni

then the distance moved by effort will be 6 unit

(sance V-Ra

50

180 (66)

56

100

5600 560 90x0 必

Since efficienay

Load

Ae in effort.

503x54 500

V.R. = D

efficiency.

100%

(3)(a)

Seeing and

(b)

Determina

of J

(1) weight of empty calorimeter » (ar) weight of calorimeter water

(make sure the amount of water Bufferent so that the heating"is immersed in it).

(111)Temperaturo of water 1

(ay) The key's is turned on, Tsuitable

current. 19, adjusted by the rheostat and the current is allowed to pass for a certain time t so that tem perature of water. increases to Ty Current

(vi) voltage

d

These are measured from the readings of the ammeter and voltmeter

Since electrical enerøv

Ivt in joules Ivt

tp calories

the initial acceleration

See he die

(b) since W.D. by effore, H.D. by load wasted work when the load is. thereased, Wei, by Load of cours rs increased, but the wasted work. increases: by a.smaller proportion sance wasted work is. the W.D. by movable part of the machine (which "Tạ constant) and .. to overcome friction (which increase: sightly with Toad")Thus the wastud -work is a smaller of the .D. by effort when

the load is increased and V.D. by load is a greater of the work done by Leffort thers life. efficiency is increased

ing gained by water and calorimeter

of calorimeter.

·Ïvt

to vapour heat loss. electrical encrov ber

electrical energy.

beat gained

55 1 00 joules.

60

cals 4.2

Heat gained by liquid fan change of state = 8.92 0.

where L = Latent heat of vaporisation.

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鄭

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佩佩

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華夢何

演溽

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分類廣告

黑風寨

珍風

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【機巧除步 ®

【關佈着步

每天元半

費用廉

收效大

5560

,52; 1 + 11 (1) where H = heat loss per min. Similarly for the second case.

4.2

4.89 L+ U (11

Solving (i) and (ii)

L = 82.6.ca1/gm.

9.6 cal/sec..

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