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Physics
WAEC / WASSCE 1989
Waves, Sound & Vibrations
Solution
Which of the following is a stringed instrument?
A
flute
B
trumpet
C
piano
D
drum
E
saxophone
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
The piano is classified as a stringed instrument because it produces sound through vibrating strings, even though it also has a keyboard mechanism.
Source: Myschool Past Questions Archive (Record #23921)
Physics
WAEC / WASSCE 1989
Current Electricity & Electric Circuits
Solution
A sound pulse sent vertically downwards into the earth is reflected from two different layers of the earth such that echoes are heard 1.2s and 1.4s. Assuming speed of the pulse is 2000ms-1, calculate the distance between the layers.
A
200 m
B
400 m
C
2400 m
D
2600 m
E
2800 m
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
X = Δvt/2 = {(2000x14)2 - (2000x12)2} = 200 m.
Source: Myschool Past Questions Archive (Record #23922)
Physics
WAEC / WASSCE 1989
Waves, Sound & Vibrations
In a wave the maximum displacement of particles from their equilibrium positions is called.
A
frequency
B
amplitude
C
period
D
wavelength
E
wave velocity
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #23923)
Physics
WAEC / WASSCE 1989
Current Electricity & Electric Circuits
Solution
A string is stretched between two points 50cm apart. It is then plucked at its center and the velocity of the wave produced is 300m/s. Calculate the number of vibrations made by the string in 1s.
A
3
B
6
C
150
D
300
E
600
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
λ = 2 x 50 = 100cm = 1m.
V = fλ, f = v/λ = 300.
Source: Myschool Past Questions Archive (Record #23924)
Physics
WAEC / WASSCE 1989
Waves, Sound & Vibrations
Which of the following is not a property of longitudinal waves?
A
compression
B
reflection
C
refraction
D
polarization
E
diffraction
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #23925)
Physics
WAEC / WASSCE 1989
Current Electricity & Electric Circuits
Solution
What is the gravitational potential due to a molecule of mass, m and at a distance, r from it? (G = gravitational constant).
A
Gm2/r2
B
Gm/r
C
Gm2/r
D
G2m2/r
E
m2/Gr2
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
The gravitational potential (often denoted as V or φ) due to a single point mass m (such as a molecule treated as a point mass) at a distance r from it is given by:
V = - \(\frac{\text{G m}}{\text{r}}\)
Where: G is the gravitational constant, m is the mass of the molecule, r is the distance from the center of the molecule to the point where the potential is being evaluated. The negative sign is conventional: gravitational potential is zero at infinity and becomes more negative (lower) as you get closer to the mass.
Source: Myschool Past Questions Archive (Record #23926)
Physics
WAEC / WASSCE 1989
Circular Motion, Gravitation & Simple Harmonic Motion
Solution
Calculate the escape velocity for a rocket fired from the earth's surface at a point where the acceleration due to gravity is 10ms-2 and the radius of the earth is 6 x 106m.
A
7.8 x 106ms-12
B
1.1 x 104ms-1
C
3.5 x 107ms-1
D
6.0 x 107 ms-1
E
1.2 x 108ms2-1
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Hint: V = √2gr = √(2x10x6x106) + 1.1 x 104ms-1
Source: Myschool Past Questions Archive (Record #23927)
Physics
WAEC / WASSCE 1989
Electrostatics & Capacitors
Solution
The electric force between two point charges each of the magnitude, q at a distance of r apart in air of permittivity is:
A
q2/4πεr
B
rε0/q2
C
4πq/ε0
D
qr2/ε0
E
\(\frac{q^2}{4\piεor^2}\)
medium Difficulty
Verified Correct Answer: Option E
Physical Principles & Numerical Solution
According to Coulomb's law, the Force between two point charges \(Q_1\) and \(Q_2\) is equal to
F = \(\frac{Q_1 Q_2}{4\pi εor^2}\)
Source: Myschool Past Questions Archive (Record #23928)
Physics
WAEC / WASSCE 1989
Atomic, Quantum, Nuclear Physics & Electronics
Solution
(a)(i) Explain the terms: photoelectric emission and threshold frequency; (ii) Einstein's photoelectric equation can be written as \(E = hf - hf_{o}\) What does each of the symbols used in the equation above represent?
(b) Calculate the frequency of the proton whose energy is required to eject a surface electron with a kinetic energy of \(1.97 \times 10^{-16} eV\) if the work function of the metal is \(1.33 \times 10^{-16}eV\). \((1 eV = 1.6 \times 10^{-18}J; h = 6.60 \times 10^{-34}JS)\).
(c) In a photoelectric cell, no electrons are emitted until the threshold frequency of light is reached. Explain what happens to the energy of the light before emission of electrons begins. State one factor that may affect the numbers of emitted electrons.
(d) Explain what is meant by the duality of matter, illustrating your answer with observation phenomena.
A
q2/4πεr
B
rε0/q2
C
4πq/ε0
D
qr2/ε0
E
\(\frac{q^2}{4\piεor^2}\)
medium Difficulty
Verified Correct Answer: Option E
Physical Principles & Numerical Solution
a(i) Photoelectric emission occurs when electrons are emitted from the surface of metal plate when it is illuminated by light of sufficient high frequency. Threshold frequency is the minimum frequency of the illuminating light which will just be sufficient to cause photoelectric emission. Below this frequency, electrons will not be emitted.
(ii) In the Einstein's photoelectric equation \(E = hf - hf_{0}\),
E - is the maximum kinetic energy of the emitted electron ;
hf - is the energy of the illuminating light;
\(hf_{0}\) - is the work function. It represents the minimum energy required to liberate electrons from the surface of the metal
\(f_{0}\) - is the threshold frequency.
(b) Using \(E = hf - hf_{0}\)
\(f = \frac{E + hf_{0}}{h}\)
(d) The duality of matter means that matter can exhibit wave properties as well as have particle properties. This double nature of matter is general in nature e.g. particles like electrons can have wave properties. Waves such as X-rays can have particle properties. This is equally illustrated by photoelectric effect.
De Broglie equation for the waves carried with particle is
\(\lambda = \frac{h}{mv} = \frac{h}{p}\)
mv = p is momentum of particle of mass m; h - planks constant.
Source: Official Exam / Past Question Archive
Physics
UTME / JAMB 1989
Current Electricity & Electric Circuits
Which of the following is a set of vectors?
A
force, mass and moment
B
acceleration, velocity and moment
C
mass, weight and density
D
mass, volume and density
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #28304)
Physics
UTME / JAMB 1989
Scalars, Vectors & Relative Motion
Solution
The magnitude of the resultant of two mutually perpendicular forces, F1 and F2 is 13N, if the magnitude of F1 is 5N, what is the magnitude of F2?
A
2.6N
B
6.0N
C
12.0N
D
18.0N
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
(13)2 = 52 + (F2)2
F2 = 12N
Source: Myschool Past Questions Archive (Record #28307)
Physics
UTME / JAMB 1989
Current Electricity & Electric Circuits
Solution
Two points on a velocity time-graph have coordinates (5s, 10ms-1) and (20s, 20ms-1). Calculate the mean acceleration between the two points
A
0.67ms-1
B
0.83ms-1
C
1.50ms-1
D
2.00ms-1
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
a = \(\frac{v - u}{\Delta t}\)
a = \(\frac{20 - 10}{20 - 5}\)
a = 0.67ms-1
Source: Myschool Past Questions Archive (Record #28311)
Physics
UTME / JAMB 1989
Elasticity, Density, Pressure & Fluids
A thin film of liquid is trapped between two glass plates. The force required to pull the plates apart will increase if the
A
surface tension of the liquid is reduced
B
perpendicular distance between the plates is increased
C
area of the liquid surface in contact with the plates is increased
D
pressure of the air is decreased
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #28316)
Physics
UTME / JAMB 1989
Work, Energy, Power & Simple Machines
Solution
A block-and-tackle system is used to lift a load of 20N through a vertical height of 10m. if the efficiency of the system is 40%, how much work is done against friction?
A
80J
B
120J
C
300J
D
500J
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Efficiency = \(\frac{output}{input}\) x 100
40 = \(\frac{20\times10}{input}\) x \(\frac{100}{1}\)
input = 500J
work against friction = input - output
= 500 - 200 = 300J
Source: Myschool Past Questions Archive (Record #28321)
Physics
UTME / JAMB 1989
Elasticity, Density, Pressure & Fluids
Which of the following devices are used to measure pressure? i. Aneroid barometer. ii. hydrometer. iii. hygrometer. iv. manometer.
A
i and iii
B
ii and iii
C
iii and iv
D
i and iv
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #28322)