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S4 PHYSICS
1. a) Differentiate between a vector and scalar quantity. Give two examples of each case.
wall
0.8m
smooth plane
2.
Rough horizontal plane
p
A ball A of mass 2 kg is released from a wall at a height of 0.8m above a rough
horizontal surface along a smooth inclined plane as shown above
Find the velocity of the ball as it strikes point P.
Find also the frictional force required to bring the ball to a rest in a distance of 2m
along the rough surface.
3. (a) State the laws of refraction of light
i. A coin is placed at the bottom of a tall gas jar. When the gas jar is filed with
paraffin to a depth of 32.4 cm, the coin is apparently seen displaced 9.9 cm from
the bottom. What is the refractive index of paraffin?
ii. Paraffin has a greater refractive index than water. What can you say about the
relative velocity of light in paraffin and in water?
4. a) What is meant by the term terminal velocity?
b). A small steel ball is allowed to fall centrally down a tall cylinder containing
lubricating oil.
i. Sketch the velocity time graph for the motion of the ball.
ii. Describe the features of the graph.
c) A solid of dimensions 2cm by 2cm by 2cm has a mass of 0.056kg. The solid is
completely immersed in a liquid of density 850 kgm-3. Find the:
ii. Volume of the liquid displaced.
iii. Weight of liquid displaced
iv. Apparent loss in weight
d) i) Distinguish between adhesion and cohesion
ii. Explain the observation that when mercury and water are separately poured on
glass, mercury does sot wet glass but water does.
e) A ball has a mass of 0.5kg. It is released from rest from a cliff and strikes the sea
bed with a velocity of 10 ms-1. Calculate:
i. The height of the cliff,
ii. The kinetic energy of the ball when it strikes the sea.
5. (a)Define:
i) Inertia of a body
ii) Momentum
b) State Newton’s second law of motion.
A body of mass 20 kg moving with uniform acceleration has an initial momentum of 200
kgms-1 and after 10 seconds the momentum is 300 kgms-1. What is the acceleration of the
body?
c)Explain why a passenger standing on the floor of a lorry jerks backwards when the
lorry suddenly starts moving forward.
d)A body is fired horizontally with a speed of 30 ms-1 from a cliff 500 m above the
ground. Calculate;
i.
ii.
the time taken before the body hits the ground
the horizontal distance traveled.
(e) A sprint cyclist starts from rest and accelerates at 1m/s2 for 20 seconds. He then
travels at a constant speed for a minute and finally comes to rest at a rate of 2 ms-2.
i. Draw a graph of speed against time for the motion.
ii. From your graph deduce the total distance traveled.
iii. Find his maximum speed in kmh-1
iv. Find the average speed for the whole journey.
6. What is meant by the following terms as applied to lenses.
i). Principal focus ii) optical centre
iii) focal length
magnification
iv). Linear
b) i). Explain how total internal refection occurs. State the conditions necessary for it do
occur.
ii. State the applications of total internal refection.
c) An object 1cm tall is placed 12 cm in front of a converging lens of focal length 10 cm.
by graphical method; determine the position and nature of the image formed.
d) With the aid of a labeled diagram, explain the operation of a lens projector.
e) Explain the terms rectilinear propagation of light. Describe an experiment to verify
the phenomenon.
f) Show with the aid of a diagram the nature of the image formed in:
(i) A diverging lens (ii) Convex mirror.
7. a). A bucket of mass 20 kg is raised a distance of 5.0 m from a well by means of a
wheel and axle arrangement. The radius of the wheel is 25.0cm and the radius of the
axle is 5.0cm. It requires a force of magnitude 50N applied to a handle at the rim of
the wheel to raise the bucket. Calculate
a. The velocity ratio,
b. The efficiency; of the wheel and axle.
b) According to the kinetic theory, what are the physical properties common to all
gases? What is the internal effect of raising the temperature of a gas? In what ways
does a gas in a container exert pressure on the walls?
c) Describe the construction and use of a simple mercury barometer.
8. a) Define the term refractive index of a medium.
b) Given that the refractive index for a medium is 1.35. Use geometrical construction to
find the angle of refraction for a ray moving from air to the medium, if the angle of
incidence is 31o.
c) A ray of monochromatic white light passes through a glass prism. Explain what is
observed in the emergent ray. Describe how the observation above may be obtained in
is pure form.
d) Distinguish between primary and secondary colours as used in science. Give
examples in each case.
e) A boy putting on a yellow tie with blue spots passes first in red light then in green
light and last in yellow light. What colour changes take place in the appearance of the
tie?
f) Explain why the sky appears blue.
9.A galvanometer has a resistance of 5Ω and a range of 0- 40 mA. Find the resistance of
the resistor which must be placed in parallel with the galvanometer if a maximum current
of 10A is to be measured.
b) State ohm’s law. Describe with the help of a suitable diagram how you can verify
ohm’s law. States the limitations of ohm’s law.
2Ω
D
2V
5Ω
Four resistors are connected in the circuit as shown in the figure above. Assuming the
internal resistance of the cell and ammeters are negligible find:
i. The total resistance of the circuit
ii. The current through ammeter D
iii. Current through ammeter C
iv. Power dissipated in the 3Ω resistor.
c) A heater is rated 750W, 240 V.
i. What does the statement 750W, 240V mean?
ii. Calculate its resistance
iii. Find the cost of running three such heaters for four hours a day for a week given that
the cost of electric energy is 45/= per unit.
d) A coil of resistance wire is immersed in a liquid in a calorimeter of total heat capacity
950 JK-1. If the temperature rises from 9oC to 39oC in 5 minutes when a steady current
of 4 A is passed, find:
i) the resistance of the coil
ii) the p.d across it.
10a). A moving coil milliameter of a resistance 10Ω gives a full scale deflection when a
current of 50mA flows in it. This milliameter may be converted into a d.c voltmeter to
read 15V by the addition of a resistance. Draw a diagram to illustrate how this may be
done and calculate the value of the resistance.
Explain the use of the instrument as a voltmeter.
b) A galvanometer of resistance 6Ω gives a full scale deflection when a current of 15
mA flows in it. How may it be converted to an ammeter giving a full–scale deflection
for a current of 1.5A?
c) State the advantages of using a moving coil galvanometer.
11a). Give an account of the structure and action of the simple cell and dry cell.
b) Explain the terms polarization and local action as applied to cells. Show how these
defects are overcome in one practical form of cell.
c) i). Name the advantages which a lead acid accumulator has over a dry cell.
ii. Explain how a lead acid accumulator can be charged when it has run down.
iii. Outline the precautions regarding the care of a lead –acid accumulator.
12a). What is meant by the term electromagnetic induction?
State the laws of electromagnetic induction and out line the ways of increasing the
magnitude of induced e.m.f in a coil. Also define the terms self induction and mutual
induction.
b) Describe the structure and mode of action of an a.c transformer.
Differentiate between the types of transformers. Describe the causes of energy losses in a
transformer. How can these losses be minimized.
c) A transformer of efficiency 80% is connected to a 240V a.c supply to operate a heater
of resistance 200Ω. If the current in the primary circuit is 5A.
i. Calculate the p.d across the heater.
ii. If the transformer is cooled by oil of specific heat capacity 2100 Jkg-1k-1 and
temperature of oil raises by 25 K in 3 minutes, find the mass of the oil in the
transformer.
13.Define the following terms as applied to earth’s magnetism
i) Magnetic north
ii) magnetic meridian
iii) Geographical meridian
iv) magnetic field
v) Magnetic saturation
vi) magnetic variation/declination
vii) Angle of dip
viii) isogonals
(ix) Isoclinals
b) Sketch the resultant magnetic field patterns for the following:
i. Two bar magnets placed with S-poles facing each other
ii. Two bar magnets placed close to each other and are parallel
iii. A bar magnet placed in the earth’s magnetic field
iv. A wire carrying current (inside and out)
v. Two wires carrying current in opposite directions
vi. Two wires carrying current in the same direction
vii. Current through a circular coil
viii. a solenoid
ix. a wire carrying current in the earth’s field
x. Two bar magnets paced with opposite poles close together and are parallel
c) Give the ways in which the strength of a magnet can be increased. With the aid of a
labelled diagram, describe the principle of action of a moving coil loudspeaker/receiver.
14.(a) What is meant by the following terms
i) Standing wave
ii) wave length
iii) reverberation
b) A fishing boat uses ultra sound of frequency 6.0 x 104 Hz to detect fish directly below.
Two echoes of the ultra sound are received, one after 0.9 s coming from a fish and
another after 1.2 s coming from the sea-bed. If the sea bed is 84m below the ultra
sound transmitter and receiver, calculate:
i. The speed of ultrasound in water
ii. The wave length of ultra sound waves in water
iii. The depth of the fish below the boat
c) Distinguish between light and sound waves.
d) A tuning fork of frequency 512 Hz produces resonance in a tube of length 10.5 cm
and also in one of length 91.5 cm.
Calculate.
i.
ii.
The wave length of the sound in the air column
The velocity of sound in the air column.
15a) What is meant by the following terms as applied to thermometry:
i) Lower fixed point
ii) upper fixed point
iii) Absolute zero
iv) fundamental interval.
b) i). Describe how the fixed points of a temperature scale may be obtained.
c) Give the reasons for and not for using water as a thermometric liquid.
ii. Give the advantages and disadvantages of using mercury over alcohol.
d) With the aid of a labeled diagram, describe an experiment to show the relationship
between the volume and the temperature of a fixed mass of gas at atmospheric
pressure.
A cylinder with a movable piston contains 0.25m3 of air at 290C. Calculate the volume of
the gas if it is cooled to -730C at constant pressure.
e) Use the kinetic theory of matter to explain cooling by evaporation.
What is meant by the term specific heat capacity of a substance?
Describe the ways of determining the specific heat capacity of a metal block such as
aluminum.
A waiter pours 0.25 kg of water initially at 750C to a copper mug of mass 0.30 kg initially
at 20oC. The mug and water later attain a temperature of θ0C. Find the value of θ. (take
s.p.c of copper = 400 Jkg-1K-1, sp.h.c of water = 4200 Jkg-1k-1).
b) What is an ideal gas? Distinguish between a real gas and an ideal gas.
c) Describe the principle of operation of a refrigerator.
Describe what is meant by the term green house effect