s6 Physics p1 Buganda
s6 Physics p1 Buganda
s6 Physics p1 Buganda
PHYSICS
Paper 1
July/Aug. 2018
2½ hrs
INTERNAL MOCK EXAMINATINS – 2018
Uganda Advanced Certificate of Education
Physics Paper 1
2 hours 30 minutes
INSTRUCTIONS TO CANDIDATES:
Attempt five questions, including at least one but not more than two questions from each of the sections A, B and C.
Any additional question(s) answered will not be marked.
Non-programmable scientific calculators may be used.
Assume where necessary:
Acceleration due to gravity, g = 9.81ms-2
Electronic charge, e = 1.6 × 10-19C
Electron mass = 9.11 × 10-31kg
Mass of the earth = 5.97 × 1024kg
Plank’s constant, h = 6.6 × 10-34Js
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SECTION A
2
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(ii) = (03 marks)
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(c) A horizontal spring of force constant 300, fixed at one end has a mass of
3- attached to the free end and resting on a smooth horizontal surface. The
mass is pulled through a distance of 5.0. and released. Calculate;
(i) angular speed, (02 marks)
(ii) maximum velocity attained by the vibrating body. (02 marks)
(iii) acceleration when the body is half way towards the centre from its initial
position. (02 marks)
(d) (i) What is meant by a couple in mechanics? (01 mark)
(ii) State the conditions for equilibrium of a system of coplanar forces.
(02 marks)
(e) Explain why a person standing near a railway line is sucked towards the
railway line when a fast moving train passes. (03 marks)
3
Turn Over
SECTION B
5. (a) (i) Define thermal conductivity. (01 mark)
(ii) Explain the mechanism of heat transfer in metals. (03 marks)
(b) A double glazed window has two glass sheets of thickness 5.0 , separated
by a layer of air of thickness 1.2 . If the two inner air – glass surfaces have
steady temperatures of 25 0 and .5 0 respectively, find the:
/ /
(ii) Use the expression in (d) (i) above to deduce Dalton’s law of partial
pressures. (03 marks)
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7. (a) Define a thermometric property and give two examples. (02 marks)
(b) The resistance, 67 of platinum varies with temperature & / 0 as measured by a
constant volume gas thermometer according to the equation:
67 = 50.0 + 0.17& + 3.0 × 10 &
(i) Calculate the temperature on the platinum scale corresponding to 60/ 0
on the gas scale. (06 marks)
(ii) Account for the difference between the two values and the temperature
at which they agree. (02 marks)
(c) Use the kinetic theory of matter to explain the following observations:
(i) Saturated vapour pressure of a liquid increases with temperature.
(03 marks)
(ii) Saturated vapour is not affected by a decrease in volume at constant
temperature. (03 marks)
(d) An ideal gas of volume 100. at s.t.p expands a diabatically until its
pressure drops to a quarter its original value. Find the new volume and
temperature if the ratio of the principal specific heat capacities is 1.4
(04 marks)
SECTION C
8. (a) (i) What is meant by the terms: radio active, decay, half life and decay
constant? (03 marks)
;<
(ii) Show that the half –life : of a radio isotope is given by : = where >
$ $ =
is the decay constant. (Assume the decay law , = ,?@ =A
).
(03 marks)
(b) With the aid of a diagram describe the structure and action of a diffusion cloud
chamber. (05 marks)
(c) The radio isotope <C4B decays by emission of D − particles. The half – life of
the isotope is 28.8 year. Determine the activity of 1 of the isotope.(05 marks)
(d) (i) What are cathode rays? (01 mark)
(ii) An electron accelerated by a G. H of 1000I passes through a uniform
electric field intensity crossed with a uniform magnetic field of flux
density 0.3'. If the electron emerges undeflected, calculate the electric
field intensity. (03 marks)
5
Turn over
9. (a) (i) Define space charge as applied to thermionic diodes. (01 mark)
(ii) Draw anode current – anode voltage curves of a thermionic diode for
two different filament currents and explain their main features.
(06 marks)
(b) Derive the expression for the amplification factor J in terms of anode
resistance, 6K and mutual conductance, L for a triode valve. (03 marks)
(c) A triode with mutual conductance 3 I and anode resistance of 10-M is
connected to a load resistance of 20-M. Calculate the amplitude of the output
signal if the amplitude of the input signal is 30 I. (04 marks)
(d) (i) What is a photon? (01 mark)
(ii) Explain using the quantum theory, the experimental observations on
photo electric effect. (05 marks)
10. (a) A beam of N - particles is directed normally to a thin gold foil. Explain why
(i) most of the alpha particles past straight through the foil,(02 marks)
(ii) few alpha particles are deflected through angles more than 90/ .
(02 marks)
(b) Calculate the least distance of approach of a 4.0O@I alpha particles to the
nucleus of a gold atom. (Atomic number of gold = 79). (04 marks)
(c) Explain, using suitable sketch graphs, how B – ray spectra in an B – ray tube
are produced. (06 marks)
(d) A beam of B – rays of wave length 9 × 10 is incident on a sodium
chloride crystal of interplanar separation 9.0 × 10 C . Calculate the first
order diffraction angle. (03 marks)
(e) (i) Distinguish between nuclear fussion and nuclear fission. (02 marks)
(ii) State the conditions necessary for each of the nuclear reactions in (e) (i)
to occur. (01 mark)
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END