WAEC - Physics (1998)

1
which of the following pairs of physical quantities comprises vectors?
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(C)
friction and momentum
2
A piece of stone attached to one end pf string is whirled round in a horizontal circle. When the string is suddenly cut, the stone will
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(D)
fly off in a direction tangential to the circular path
3
The term torque means
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(A)
the moment
4
A rectangular block of wood floats in water with two-thirds of its volume immersed. When placed in another liquid, it floats with half of its volume immersed. Calculate the relative density of the liquid
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(B)
1.33
5
As the end Q of the plank is raised, the component of W, normal to plank, will
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(B)
decrease
6
If \(\theta\) is equal to \(\alpha\) at the time the box is just about to slide down the plank, the coefficient of static friction between the plank and box is
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(C)
tan\(\alpha\)
7
I the box is pulled from P to Q, which of the following expresses the velocity ratio of the inclined plane?
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(E)
PQ/QR
8
a pilot records the atmospheric pressure outside his plane as 63cm of Hg while a ground observer records a reading of 75cm of Hg with his barometer. Assuming that the density of air is constant, calculate the height of the plane above the ground. (take the relative densities of air and mecury as 0.00136 and 13.6 respectively)
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(D)
1200m
9
An object is protected with a velocity of 100m^-1 at an angle of 60^o to the vertical. Calculate the time taken by the object to reach the highest point (Take g as 10ms^-2
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(B)
8.7s
10
The earth is not a perfect sphere because its equatorial axis is longer than the polar axis. where on the earth's surface would an object have its greatest weight?
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(D)
at either pole
11
a ball of mass 5.0kg hits a smooth vertical wall normally with a speed of 2m^-1 and rebounds with the same speed. Determine the impulse experienced by the ball
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(A)
20.0kgm^-1
12
An object is heated from 30ºC to 57ºC. The increases in its temperature on the Kelvin scale is
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(B)
27k
13
The lower and upper fixed points of a mecury-in-glass thermometer are marked Y and 180mm respectively. On a particular the mecury meniscus in the thermometer rises to 45mm. If the corresponding reading on a scale is 10o, calculate the value of Y.
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(C)
30mm
14
A piece of brass of mass 170kg has its temperature raised from 0ºC to 30ºC. Calculate its increase in volume, given the density of brass at 0 °C as 8.5 x 103kgm\(^3\) and its cubic expansivity as 5.7 x 10\(^{-5}\)k\(^{-1}\)
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(C)
3.4 x 10^-5m³
15
The average kinetic energy of the molecules of a perfect gas is directly proportional to the
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(C)
kelvin temperature of the gas
16
How much heat is emitted when a body of mass 200g cools from 37^oC to 31^oC? (specific heat capacity of the body = 0.4Jg^-1K^-1,)
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(C)
480J
17
If the cubic expansivity of brass between 27^oC and 100^oC is 5.7 x 10^-5K^-1, What is its linear expansivity?
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(B)
1.90 x 10^-5K^-1
18
Air at temperature 527^oC and pressure 30 atmospheres is admitted into the cylinder of an engine. Calculate the pressure of the gas when it has expanded to 5 times its volume and cooled to 127^oC as it leaves the engine
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(C)
3.0 atmospheres
19
The inside of a vacuum flak is usually coated with silver to reduce heat loss by
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(B)
radiation
20
Dry oxygen is trapped by a pellet of mercury in a uniform capillary tube which is sealed at one end. The length of the column of oxygen at 27^oC is 50cm. if the pressure of the oxygen is constant, at what temperature will the length be 60cm?
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(D)
87.0^oC
21
A waterfall is 1260m high. Calculate the change in temperature of a quantity of water that falls from the top to the bottom of the waterfall. (Neglect heat losses to the surroundings, take g as 10m-2 and specific heat capacity of water as 4200Jkg-1K-1)
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(B)
3.0^oC
22
A piece of metal is heated until it becomes red-hot, it is then quickly transferred into a beaker containing boiling water. What effect will this have on the boiling water?
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(C)
the rate of vaporisation of the boiling water increases
23
A 90-W immersion heater is used to supply energy for five minutes. The energy supplied is used to completely melt 180g of a solid at is melting point. Neglecting energy losses to the surroundings, calculate the specific latent heat of fusion of the solid
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(E)
150Jg^-1
24
If an ebonite rod is rubbed with fur
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(D)
the ebonite rod will be negatively charged while the fur will be positively charged
25
An eclipse of the sun by the moon occurs when the sun, the moon and the earth are in a straight line and the
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(C)
moon is between the sun and the earth
26
The phenomenon which occurs when light changes direction as it passes from one medium to another is called
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(E)
refraction
27
What is the image distance of an object placed at a distance of 2f from a converging lens of focal length f?
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(D)
2f
28
The images formed by diverging lenses are always
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(B)
diminished, virtual and errect
29
A converging lens of focal length 5cm is used as a magnifying glass by a man whose nearpoint is 35cm. Calculate the magnification given by the lens
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(C)
6
30
An astronomical telescope having an objective of focal length 100cm and an eyepiece of focal length 10cm is used in normal adjustment, calculate the separation of the lenses
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(C)
1.10m
31
A lantern gives an image of 3m square of a slide 7.62cm square on a screen. If the screen is 10m from the projection lens of the lantern, calculate the focal length of the lens
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(C)
24.8cm
32
The intensity of light falling on the film in a camera depend on the i. brightness of the object. ii. diameter of the aperture stop. iii. speed of the shutter. Which of the statements is/are correct/
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(E)
iii only
33
the shortest length of the air column in a resonance tube at resonance is 0.12m and the next resonance length is 0.37m. calculate the frequency of vibration given that the speed of sound in air is 340m^-1
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(C)
680Hz
34
A sonometer wire under a tension of N10N, produces a frequency of 250Hz when plucked. Keeping the length of the wire constant, the tension is adjusted to produce a new frequency of 350Hz. Calculate the new tension
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(B)
19.6N
35
Calculate he wavelength of a note which is one octave lower than a note of 256Hz in a medium in which the speed of sound is 352ms^-1
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(B)
1.38m
36
Which of the following are both mechanical and transverse?
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(D)
water waves
37
An electromagnetic wave of frequency 5.0 x 10¹⁴Hz, is incident on the surface of water of refractive index \(\frac{4}{3}\). Taking the speed of the wave in air as 3.0 x 10⁸ms^-1, calculate the wavelength of the wave in water.
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(E)
4.5 x 10^-7m
38
The gravitational force of the moon is one-sixth that of the earth. If a body weighs 6.0N on the moon. Calculate its weight on the earth
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(A)
36.0N
39
In the electrical method of magnetisation, the polarity of the magnet depends on the
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(B)
direction of current
40
A cell of e.m.f. 1.5v is connected in series with a resistor of 3\(\Omega\). A high resistance voltmeter connected across the cell registers only 0.9v. Calculate the internal resistance of the cell
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(D)
2.0\(\Omega\)
41
Calculate the resistance of the filament of lamp rated at 240V 60W
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(C)
960\(\Omega\)
42
The diagram above illustrates a freely suspended bar magnet NS hanging from a point in a horizontal ceiling. The thread used for suspending the magnet and the axis of the magnet are as indicated on the diagram. The angle marked \(\theta\) is called the angle os
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(E)
dip
43
Lenz's law of electromagnet states that
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(D)
the induced current in a conductor is in such a direction as to oppose the change producing it
44
A proton of charge 1.6 x 10\(^{19}\)C is projected into a uniform magnetic field of flux density 5.0 x 10\(^5\)T. If the proton moves parallel to the field with a constant speed of 1.6 x 10\(^6\)ms\(^{-1}\), calculate the magnitude of the force exerted on it by the field
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(A)
0.0N
45
The direction of the magnetic field at a point in the vicinity of a bar magnetic is
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(E)
the direction towards which the north pole of a compass needle would point
46

The diagram below illustrates an a.c.source of 50V(r.m.s.), \(\frac{100}{\pi}\)Hz connected in series with an inductor of inductor of inductance L and a resistor of resistance R. The current in the circuit is 2A and the p.d across L and R are 30V and 40V respectively. Calculate the power factor of the circuit
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(C)
0.80
47
The diagram below illustrates an a.c.source of 50V(r.m.s.), \(\frac{100}{\pi}\)Hz connected in series with an inductor of inductor of inductance L and a resistor of resistance R. The current in the circuit is 2A and the p.d across L and R are 30V and 40V respectively. Calculate the average power dissipated in the circuit
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(B)
80W
48
Use the following data to determine the length L of a wire when a fore of 30N is applied, assuming Hooke's law is obeyed
\(\begin{array}{c|c}\text{Force applied/N} & 0 & 5 & 10 & 30\\ \hline \text{length of wire/mm} & 500.0 & 500.0 & 501.0 & L \end{array}\)
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(C)
503.00mm
49
Which of the following explains the concave meniscus of water in a clean glass tube? the
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(A)
adhension between water and glass molecules is greater than the sdhension between water molecules
50
An electron is accelerated from rest through a potential difference of 70kV in a vacuum. Calculate the maximum speed acquired by the electron (electronic charge = -1.6 x 10^-19; mass of an electron = 9.1 x 10^-31kg)
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(C)
1.57 x 10⁸ms^-1
51
When light from a source is sent through a gas
I. Certain wavelengths are absorbed.
II. an emission line spectrum results.
III. A dark line is left.
Which of the following is/are correct?
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(D)
i and iii only
52
The diagram above represents a section of a pair of vernier calipers. The reading on the instrument is
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(C)
5.26
53
The process of increasing the energy of an atom via inelastic collision with an electron is known as
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(B)
excitation
54
A radioactive nuclide of proton number X emits a \(\beta\)-particle to form a new nuclide to proton number Y. The correct equation relating X and Y is
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(B)
X = Y + 1
55
The frictional effect between the layers of a moving fluid is called
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(E)
viscosity