CANDIDATE NO: _____________________________________________________________________________________
CATHOLIC SCHOOLS ACADEMIC UNION (CASAU) 2020
FORM SIX PRE-NATIONAL EXAMINATION
131/2
PHYSICS PAPER 2
(For School Candidates Only)
Wednesday 12th February, 2020 a.m.
Time: 3 Hours
Instructions
1. This paper consists of six (6) questions; answer any five (5) questions from thy paper.
2. Each questions caries a total of 20 marks.
3. Cellular phones are not allowed in the exam room.
4. Write your exam number on every page of your answer sheet(s).
5. The following information may be used.
a)
b)
c)
d)
e)
f)
g)
h)
i)
j)
Coefficient of linear expansion of copper α = 8.0 x 10-6/ C.
Bulk modulus of elastic of copper β = 3.6 x 1011 Nm-2.
1 atmosphere = 760mmHg
Electronic charge = 1.6 x 10-19C.
Mass of electron = 9.1 x 10-31kg.
Permittivity of free space μo= 4𝜋 x 10-7 ltm.
Permittivity of force space E0 = 8.854 x 10-12SI
1
= 9.0x109mF
4 o
Plancks canstant, h=6.62 x 10-34JS
Speed of light, C = 3.0x108m/s.
Page 1 of 5
CASAU F.6 - 2020
CANDIDATE NO: _____________________________________________________________________________________
QUESTIONS.
1. (a) (i) Distinguish between static pessure, dynamic pressure and total pressure when applied to
streamline or laminar fluid flow and write down expressions at a point in the fluid
interms of the fluid velocity V, the fluid density  , Pressure P, and height h, of the point
with respect to datum.
(03 Marks)
(ii) The static pressure in a horizontal pipe line is 4.3x104Pa, the total pressure is 4.7 x 104 Pa
the area of cross section is 20cm2. The fluid may be considered to be incompressible and
non-viscous and has a density of 1000kgm-3. Calculate the flow velocity and the volume
flow rate in pipeline.
(03 Marks)
(b) (i) From Newton’s Law of viscosity determine the dimensions and possible units of
coefficient of viscosity.
(03 Marks)
(ii) In an experiment to determine the coefficient of viscosity of motor oil, the following
measurement are made.
Mass of glass sphere = 1.2 x 10-4kg.
Diameter of sphere = 4.0 x 10-3m.
Terminal velocity of sphere= 5.4 102 m / s
Density of oil = 860kgm-3
Calculate the coefficient of viscosity of the oil.
(c) (i) Briefly explain the carburetor of a car as applied to Bernoulls theorem
(03 Marks)
(02 Marks)
(ii) Three capillaries of the same length but with internal radii 3R, 4R and 5R are connected in
series and a liquid flows through them under streamline conditions. If the pressure across
the third capillary is 8.1mm of liquid. Find the pressure across the first capillary
(03 Marks)
(d) Give reasons for the following observations as applied in fluid dynamics.
i) A flag flutter when strong winds are blowing an a certain day.
(01 Mark)
ii) A parachute is used while jumping from air plane.
(01 Mark)
iii) Hotter liquids flows faster than cold one
(01 Mark)
2. (a) (i) Briefly explain how beats are found
(02 Marks)
(ii) What is the difference between progressive wave and stationary wave?
(03 Marks)
(iii) A man standing in front of a mountaiin beats a drum at regular intervaals. The drumming
rate is gradually increased and he finds that the echo is not heard distinctly when the rate
becomes 40 per minute. He then moves near to the mountain by 90 metres and finds that
the echo is again not heard when the drumming rate becomes 60perminutes. Calculate the
distance between the mountain and the initial position of man and the velocity of sound.
(03 Marks)
Page 2 of 5
CASAU F.6 - 2020
CANDIDATE NO: _____________________________________________________________________________________
(b) (i) Give any two applications of ultrasonic as applied to sound waves
(02 Marks)
(ii) Ultrasound of frequency 4.0 Mtlz is incident at an angle of 300C to a blood vessel of
diametre 1.6mm. If a Doppler shift of 3.2 kHz is observed.Calculate the blood flow
velocity. Assume that the speed of ultra sound is 1.5 km51
(03 Marks)
(c) The incident parallel light is a monochromatic beam of wavelength 450nm. The two slits A
and B have their centres a distance of 0.3mm apart. The screen is situated a distance of 2.0m
from the slits.
(i) Calculate the spacing between fringes observed on the screen.
(02 Marks)
(ii) How would you expected the pattern to change when the slits A and B are each made
wider?
(02 Marks)
(d) Calculate the radius of cultivature of a plano convex lens used to produce Newtons rings with
a flat glass plate if the diameter of the tenth dark ring is 4.48mm, viewed by normally
reflected light of wavelength 5.0 x 10-7m. What is the diameter of the twentieth bright ring?
(03 Marks)
3. (a) (i) Why is a soap solution being a better cleaning agent than ordinary water?
(ii) Why are the falling rain drops being spherical?
(iii) Briefly explain the factors affecting the surface tension
(02 Marks)
(02 Marks)
(02 Marks)
(b) Two spherical soap bubles cambine if V is the change in volume of the contained air, A is the
change in total surface area, then show that ;
(03 Marks)
3Pa V + 4AT =0 Where T is the surface tension and Pa is the atmospheric pressure
(c) (i) Why do spring balances show wrong reading after they have been used for a long time?
(02 Marks)
(ii) Why spring made of steel and not of copper?
(02 Marks)
(iii) Why do bridges declared unsafe after long use?
(02 Marks)
(d) (i) Calculate the pressure required to stop the increase in volume of copper block when it is
heated from 500C to 700C.
(02 ½ Marks)
3
(ii) An electric bulb of volume 250cm was sealed off during manufacture at a pressure of 103
mm of Hg at 270C. Find the number of molecules in the bulb.
(02 ½ Marks)
4. (a) (i) A charge q is placed at the centre of the line joining two charges (each of magnitude Q)
−𝑄
prove that the system of the three charges will be in equilibrium if q = 4
(02 Marks)
(ii) Two small equal charges 2.5 x 10-8C are placed at A and B. The charge at A is positive
and the charge at B is negative AB is 6cm. Find the force on a charge 1.0x10-8C placed at
P. where P is 4cm from the line AB along a perpendicular bisector XP
(03 Marks)
Page 3 of 5
CASAU F.6 - 2020
CANDIDATE NO: _____________________________________________________________________________________
(b) (i) Briefly explain what is the difference between Electric field and Electric potential?
(02 Marks)
(ii) Two electric charges q and 4q are placed at a distance of 6a apart on a horizontal plane.
Find the locus of the point on the line joining the two charges where the electric field is
zero.
(03 Marks)
(c) (i) Briefly explain what is the equipotential surface
(02 Marks)
𝑆𝑅 2
(ii) Use Gauss’s theorem, Show that Electric field outside a charged sphere is E = 𝐸
0𝑟
2
(02 Marks)
(02 Marks)
(iii) Write down the properties of equipotential surface
(d) An election of charge (e) is situated on a uniform electric field strength 1.2 x 105V/M.
Find: (i) the force on the charged electron
(01 Mark)
(ii) The acceleration
(01 Mark)
(iii) The time it takes to travel 20mm from rest
(02 Marks)
5. (a) (i) State four factors upon which the magnetic induction B at any point of the field depends
(02 Marks)
(ii) Derive an expression for the flux density B at the centre of circular coil of radius r, and N
– turns placed in air carrying current I
(02 Marks)
(iii) The diameter of a 20 turns circular coil is 0.8cm and it carries a current of 3A. Find the
magnetic moment of the coil
(02 Marks)
𝑆
(b) (i) If SI is current sensitivity ad Sv is voltage sensitivity. Show that Sv = 𝑅𝐼
(02 Marks)
(ii) A galvanometer coil has 250 turns with each having the area of 1.6cm2. If the coil is in
radial field of 2.5 x 10-2T and is suspended by thin wire having a torsional constant of 5.2
x 10-9 Nm per degree.
Find the current needed to give a deflection of 600 and voltage sensitivity If the resistance
of the coil is 2𝜴.
(04 Marks)
(c) If a toroid has 1000 turns and mean radius 25cm. Find
(i) The magnetic of the toroid of when the current flow is 2A.
(ii) The magnetic field when the toroid is filled with iron of relative permeability of 100.
(03 Marks)
(d) The magnetic flux passing perpendicular to the plane of the coil and and directed into the
paper as shown by figure 1 below is varying according to the relation  B  6t 2  7t  1
Where  B is in mWb and t in seconds.
(i) What is the magnitude of induced e.m.f in the loop when t = 2seconds
(03 Marks)
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CASAU F.6 - 2020
CANDIDATE NO: _____________________________________________________________________________________
(ii) What is the direction of current through resistor R?
(02 Marks)
R
Figure 1.
6. (a) (i) What is meant by half-life of a radioactive element?
(01 Mark)
(ii) Derive an expression for the half-life given that the decay of a radioactive element is
expressed by the relation.
dN
(03 Marks)
 N , where the symbol carry their usual meaning
dt
(b) Radium atom decay by emission of ∝ – particle. Calculate the kinetic energy of ∝ particle
emitted during disintegration Process. Given that;
4
226
222
(04 Marks)
4Ra = 226.0254 a.m.u ,
2Rn = 222.0163 a.m.u and 𝐻𝑒 = 4.0026 a.m.u
2
(c) (i) Write down the uses of nuclear reactor
(03 Marks)
(ii) Determine Planck’s constant (h) if photoelectrons are emitted from a certain metal
surface by light of frequency 2.2 x 1015 Hz are fully retarded by reverse potential of 6.6V
and those emitted by light of frequency 4.6 x 1015 Hz are stopped by a reverse potential
of 16.5V
(03 Marks)
(d) (i) Write down three (3) success of Bohr’s theory
(02 Marks)
(ii) Find the radius of the first orbit of hydrogen atom and the velocity of electron in the first
orbit.
(04 Marks)
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CASAU F.6 - 2020