Physics 2005 January P3

8/11/2019 Physics 2005 January P3

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SECONDARY EDUCATION CERTIFICATE

EXAMINATION

PHYSICS

1 hour

0 7 JANUARY 2005 ( a.m. D

In addition to the 1 hour, candidates are allowed a

reading time of 10 minutes. Writing may begin

during the to-minute period.

ALL WORKING MUST BE SHOWN inyour answer booklet, since marks will be awarded

for correct steps incalculations.


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(ii) Explain, using the kinetic theory, why the pressure in a gas increases if it is compressed

at constant temperature. (8 marks)

.(b) Figure 1 below shows part of the apparatus in which dry air is trapped in a container of uniformbore, fitted with a thermometer and an electric heater. A pressure gauge, metre rule, pump and

a valve are also shown.

(i) Given that the electric heater is rated at 1600 watts, calculate the heat energy it will

deliver to the dry air in half an hour.

The dry air is initially at a temperature of 19C and a pressure of 105 kPa. The heater

is turned on for a certain period and the temperature rises to 9 SO C while-the volume is

increased to one and a quarter times its original value. Calculate the final pressure.

(iii) Explain how you would attempt to keep pressure constant while investigating Charles'

law. (12 marks)


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vertical vertical

Single DoubleScreenFilter Slit Slit

I I

3Lamp II I

(i) Explain the function of the filter, the vertical single slit and the vertical double slit,

stating why EACH of these is necessary. Describe the pattern that would be seen on

the screen. (8marks)

Displacement

fcrn

Displacement

fcrn

(i) In your answer booklet copy Table 1 on page 5and complete it showing the displacements

of the waves at common points and the sum of the displacements.


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Points Displacement of Displacement of SumofDisplacements

Wave A WaveB ofWaveA andWaveB.

t1

t2

t3

t4

ts

(n) In your answer booklet draw agraph of displacement against time, showing thesum of

the displacements of points tl

to ts against time.

(c) In a certain medium, light has a wavelength of 5.0 x 1O-7m and a speed of 1.8x 108m S-I.

Calculate thewavelength andfrequency ofthis same light when passing through anothermedium

where its speed is 1.5x 108ms-l. (4 marks)

An object issuspended at rest some distance above the surface of the earth and then allowed

to free fall to the ground under gravity. Identify the forms of energy it possesses


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(d) Inthe process of pile driving, a heavy weight falls from a great height onto a concrete or steel

column, called a 'pile'. The pile is .driven into the earth where it can become part of the

foundation ofa very tall building. .

To model the process, a short steel cylinder ofmass 100 kg, andwhose length canbe neglected,

is made to fall freely from aheight 15 m above the top of asteel rod of mass 15kg which is

sharpened at the bottom end. Initially the rod is held in place so that itjust makes contact with

a thick block of wood. After the steel cylinder falls ontherod, therod is driven into the block

of wood.

Steel cylinder

mass = 100 kg

(i) Calculate the potential energy of the steel cylinder with respect to the top of the steel

md.

(ii) Given that t he rod and cylinder move together after the impact, calculate the

instantaneous velocity of thecombined body immediately after impact.

(ill) Fri~ti~nal force brings therod and cylinderto rest after the rod has beeI:{Qriven 0.05 m

into the block ofwood.


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(ii) Use your diagram to give a brief explanation of how the loudspeaker converts electrical

signals to sound. (8 marks)

(c) If the loudspeaker is operating at an efficiency of 0.5%,calculate the sound power produced.

(4 marks)

Deduce (no calculation required) the effect which this change would have on the total power

delivered by the amplifier. (2marks)


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(a) (i)

(ii)

(iii)

(b) (i)

.~

(ii)

Inalaboratory demonstration a teacher placed this power supply in series with a resistor and asemi-

conductor diode.

What is the difference between this type of d.c. and that from abattery?

(8 marks)

If the voltage across the diode is 0.7Vand theresistor has a value ofJ.8 kQ, calculatetheMAXIMUM voltage across the resistor and thecorresponding MAXIMUM value

ofthe current flowing in the circuit. (7marks)

(c) Many modem electronic appliances require a low d.c. voltage to operate, and to satisfy this

requirement the input a.c. voltage of 156 V may be transformed before rectification. A

transformer to be used for this purpose has 648 turns on the primary. If the secondary voltage

required from the transformer is6 V,calculate the number of turns ofthe secondary circuit,

assuming the transformer tobe ideal.

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Physics 2005 January P3