CANDIDATE NO: _____________________________________________________________________________________
CATHOLIC SCHOOLS ACADEMIC UNION (CASAU) 2020
FORM SIX PRE-NATIONAL EXAMINATION
131/1
PHYSICS 1
(For School Candidates Only)
Thursday, 06th February 2020 a.m.
Time: 3 Hours
Instructions
1.
This paper consists of sections A and B
2.
Answer ALL questions from sections A and any two (2) questions from section B.
3.
Each question in section A carries 10 marks.
4.
Each question in section B carries 15 marks
5.
Cellular phones are not allowed in the examination room.
6.
Write your Examination Number on every page of your answer sheet (s)
7.
The following constants may be useful.
(a)
Acceleration due to gravity, g = 9.8 mS-2
(b)
Universal gravitational Constant, G = 6.7 x 10-11Nm2/Kg2
(c)
Radius of the Earth, Re = 6.4 x 106m
(d)
Specific heat capacity of water Cw = 4200Jkg-1 K -1
(e)
Density of water,  w = 1000kg m-3
(f)
Stefan’s constant,  = 5.67 x 10-8 wm -2 K -4
(g)
Latent heat of Ice, L = 3.35 x 105 Jkg-1
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CANDIDATE NO: _____________________________________________________________________________________
SECTION A: (70 Marks)
Answer all questions from this section.
1. (a) Briefly explain why a pricese experiment is not necessary accurate
(b) In measurement of physical quantity “X” it is recorded as: X  X  X
(i) Identify the meaning of X and X
(ii) What does the  sign signifies?
(iii) What does the record mean?
(01 ½ Marks)
(01 Mark)
(01 Mark)
(01 Mark)
(c) (i) The length, L of a field as measured by six students under similar conditions were
recorded as follows: 98.4, 99.2, 98.5, 96.7, 99.1 and 98.7m. Barring an error analysis,
Find the associated. Percentage error in the length
(02 ½ marks)
(ii) Two quantities having the same dimensions are not always added but who numbers
having the same units may always be added. With examples, briefly explain why?
(01 ½ Marks)
(iii) Explain why an equation may be homogenous with respect to its units but still be incorrect?
(01 ½ marks)
2. (a) (i) An athlete runs over a certain distance before taking a long jump. Why?
(01 ½ Marks)
o
(ii) A ball is thrown upward at an angle of 30 to the horizontal and lands on the edge of a
building that is 20m away. The top edge is 5m above the throwing point. How fast was the
ball thrown?
(02 ½ Marks)
(b) (i) Explain why Newton’s first Law of motion can be considered to be a special case of the
Newton’s second Law of Motion.
(01 Mark)
(ii) Prove that relative velocity is reversed by a head on collision
(02 Marks)
(c) A block of mass M1 = 2.0kg on a horizontal surface whose coefficient of dynamic friction is
0.2 is connected to a mass M2 = 1.0kg by a light inelastic string passing over a frictionless
pulley as shown in figure 1. Below. Find.
(i) The tension of the string
(01 ½ Marks)
(ii) If mass, M2 is initially at height of 0.5m above the floor, Calculate the time taken by mass
M1, to come to rest after the mass M2 units the floor
(01 ½ Marks)
M1
M 2
Fifure 1.
3. (a) (i) State Conditions of an oscillatory motion to be considered simple harmonic motion.
(02 Marks)
(ii) A mass of 1.8kg is placed on a rough horizontal plant form which is set into oscillation so that it
performs simple harmonic Oscillations of amplitude 4mm in the horizontal direction. If the
Coefficient of state friction between the surfaces in contact is 0.4. Calculate the maximum
frequency which can be obtained before the mass begins to slide.
(02 ½ Marks)
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CANDIDATE NO: _____________________________________________________________________________________
(b) (i) Is there any work done when a body moves in a circular path?
(01 ½ Marks)
(ii) Briefly explain why when the bus rounding a curve the passenger throws outward?
(02 Marks)
(c) A small bead is threaded an a smooth circular wire of radius r, which is fixed in a vertical
plane, the bead is projected from the lowest point of the wire with a speed √6𝑔𝑟. Find the
speed of the bead when it has turned through 60o
(02 Marks)
4. (a) A coin is placed on a gramophone record rotation at a speed of 45 rev per minute. It flies
away when the rotational speed is 50rev/m. It two such coins are placed one over the other
on the same record. At what rotational speed will both coins fly away?
(02 Marks)
(b) Briefly explain the following
(i) Why are spokes fitted in the cycle wheel?
(01 ½ Marks)
(ii) Why is it difficult to revolve a stone by tieing it to longer string than by tieing it to a shorter
string?
(01 ½ Marks)
(c) (i) If – V is gravitational Potential and g- is gravitational field strength. Show how g is related
to V.
(ii) Briefly describe the variation of the acceleration due to gravity, g inside and outside the
earth’s surface.
(01 ½ Mark)
(iii) Find the density of the Earth if the radius of the Earth is assumed to be constant.
(01 ½ Marks)
5. (a) (i) Briefly explain why it is said that “A thermometer registers its own temperature
(01 ½ Marks)
(ii) What does one require in order to establish a temperature scale?
(iii) What are two important properties which make a given physical property to be used as a
thermometric property?
(01 Mark)
(b) One junction of a thermocouple is at OoC the thermos – emf as a function of temp (𝜃) hot
junction is E(𝜃) = (20 x 10-6 – 0.02 x 10-6 𝜃) V Find the maximum value of E.
(02 Marks)
(c) (i) If the door of a refrigerator is kept open in a room. Will it make the room warm or cool?
Explain.
(02 Marks)
(ii) Show that the slope of an adiabatic change curve is given by:
dP
P
   
Where all symbols carry their usual meaning.
dV
V 
6. (a) (i) The bulb of one thermometer is spherical while that of the other is cylindrical. Both have
equal amount of Mercury. Which one will respond quickly to temperature? (01 ½ Marks)
(ii) Briefly explain why in the summer, it is not advice to wear colored or black clothes.
(01 ½ Marks)
o
o
(iii) Tea in a cup cools in 7 minutes from 60 C to 40 C. What will be the temperature of Tea
after the next 8minutes? If the temperature of the surrounding is 15oC
(02 Marks)
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CANDIDATE NO: _____________________________________________________________________________________
(b) An ice box has total wall area (including the lid) of 1.4m2 and wall thickness 1.5cm. The
thermal Conductivity of the box is about 0.02 Wm -1K-1 It is filled with water and ice at
OoC. Calculate the amount of ice that melts in one day. If the outside temperature of the
box is 30oC
(02 ½ Marks)
(c) An Iron ball having surface area of 250cm2 at a temperature of 727oC is placed in an enclosure
at 227oC. If the surface emission of iron is 0.4. Find the rate of heat radiated by the ball.
(02 ½ Marks)
7. (a) (i) Why should not the jockey be rubbed against the potentiometer wire?
(01 ½ Marks)
(b) The current in a potentiometer wire is adjusted to give a null point at 56cm with a standard cell
of e.m.f of 1.50v. Calculate the e.m.f of another cell for which the null point is obtained at
70cm.
(02 Marks)
(c) (i) What does Kirchhoff’s first and second Law implies.
(ii) A single loop Circuit contains two external resistances and two emf sources as shown in
figure 2. The internal resistances of the batteries have been neglected. Find the current in
the Circuit and total power loot resistors.
+
A
B
E1=6V
R2=10Ω
R1 = 8𝜴
D
C
E2=12V
(03 Marks)
(d) An LCR circuit has L = 10mH, R = 3𝜴 and C = I𝜇F connected in series to a source of 15V.
Find the resonant frequency and maximum current passing through the circuit. (02 ½ Marks)
SECTION B: (30 Marks)
Answer any two (2) questions from this section.
8. (a) (i) What is the importance of doping as applied to semi conductor?
(01 Marks)
(ii) Briefly explain how P – type Semiconductor are formed (Hint Use Gallium as impurity
atom).
(02 Marks)
(iii) Why transistors are mostly used in common emitter arrangement.
(01 Marks)
(b) (i) Explain the use of an opamp as a summing amplifier
(01 ½ Mark)
(ii) Name three electronic circuit in which multivibrator can be constructed
(03 Marks)
(iii) From three types of Multivibrator; briefly explain how bitable flip - flop multivibrator
used as a switch.
(01 ½ Marks)
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CANDIDATE NO: _____________________________________________________________________________________
(c) In the Circuit shown in the figure 3, the transistor used has a current gain (= 100, Load
resistor R, = 1KΩ bias resistor RB = 200KΩ, voltage applied VCC = 10V. If VCE = 5V and
VBE is negligible.
Find
(i) The values of collector current, IC
(ii) Base current, IB.
(01 Marks)
(02 Marks)
(d)
R
C
RB
Vcc = 10V
VCE = 5V
Figure. 3
9. (a) (i) What is a function of a filter circuit?
(01 Marks)
(ii) What is the difference between Zener diode and photodiode.
(01 Marks)
(iii) Write down the advantages of digital electronics
(01 Marks)
(b) From the Boolean theorems, draw the logic gate circuits of the following expressions
(i) (B + C). A
(01 Marks)
(ii) (A  B).C.D
(01 Marks)
(c) For the intergrator circuit shown in figure 4. Find the output voltage (Vo)
0.2𝜇F
10k𝛺
+15V
V. 10mV
V0
-15V
Figure 4
(04 Marks)
10. (a) (i) Name three layers at the atmosphere
(01 Marks)
(ii) What are the factors that influence the velocities of P and S waves?
(03 Marks)
(iii) The P and S waves from an earth quake with a focus near the earth’s surface travel through
the Earth at a nearly constant speed of 8km/S and 6km/sec respectively. If there is no
reflection and refraction of waves. How long is the delay between the arrivals of successive
waves at a seismic monitoring station at 900 in the latitude from the epicenter of the
earthquake?
(b) (i) Mention three types of environmental pollution.
(ii) Explain on the following climatic factors which influence plant growth.
- Temperature
- Relative humidity and Wind
(04 Marks)
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CASAU F.6 - 2020