9. Explain how, on the kinetic model, change of state can be effected without change in
temperature, although it is a common observation that a rapidly evaporating liquid
suffers a consequent drop in temperature.
10. How could you, by electrical tests, identify the two electrodes of a diode valve?
Explain.
11. Name two regions within the electro-magnetic spectrum but outside the visible range
easily studied in the school laboratory. Make a labelled sketch showing how you
would verify the law of reflection within one of these regions.
12. Describe briefly a sensitive form of electroscope which could be used to compare the
strengths of two radium sources.
SECTION 2
Candidates are advised to spend about 1| hours on this
section. Only THREE questions should be attempted
from this section. Each question carries 18 marks.
Diagrams of apparatus should be drawn wherever
appropriate.
!■ State the principle of the conservation of momentum.
Describe and explain a method of verifying this principle by experiment.
A billiard ball of mass 100 gm moving at a steady 10 cm per sec hits a second
equal but stationary ball head on.
If no kinetic energy is lost in the collision, wdiat happens to each ball?
In practice perhaps one-quarter of the original kinetic energy would be lost in
the collision. Express this fact as an equation using the symbols V and W for
the final velocities of the first and second balls—but do not solve.
Marks
(3)
(7)
(4)
(4)
tst three different physical effects which show that matter is very fine¬
grained or alternatively continuously divisible. Next describe in detail one
experiment that suggests that there is a limit to the extent to which matter can
be divided.
Gben that Avogadro’s number is 6 X 1023 and that the gram-molecular
'o ume of any gas at N.T.P. occupies 22-4 litres, calculate the average distance
e "een the centres of the gas molecules under these conditions.
speedC?n t^e ^aS Pressure aPPear to be constant if the molecules have different
(9)
(7)
(2)
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