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Physics
WAEC / WASSCE 2020
Mechanics and Properties of Matter
Diagram
Solution
The sketched graph above illustrates the heating curve of a 0.02kg of water. Determine the approximate value of the specific latent heat of vapourization of water
Attached Figure / Diagram
A
2.25 x 10\(^6\) J kg\(^{-1}\)
B
4.17 x 10\(^3\) J kg\(^{-1}\)
C
2.00 x 10\(^3\) J kg\(^{-1}\)
D
1.00 x 10\(^3\) J kg\(^{-1}\)
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
specific latent heat of vapourization is the amount of heat energy needed to change 1kg of liquid to vapour without a temperature change. The heat absorbed by the liquid at the beginning of vapourization is \(8 \times 10^3\)J and heat absorbed after the change of stage is \(53 \times 10^3\)J. therefore, the total heat energy needed to change the liquid completely to vapour is Q = \(53 \times 10^3 - 8 \times 10^3 J = 45 \times10^3\)J
Recall, Q = mL
Where, L = specific latent heat of vapourization
Q = mL
L = \(\frac{ Q}{m}\) = \(\frac{ 45 \times 10^3}{0.02}\)
L = \(2.25 \times10^6JKg^{-1}\)
Source: Myschool Past Questions Archive (Record #59465)
Physics
WAEC / WASSCE 2020
Mechanics and Properties of Matter
In the hydraulic press, the force F applied is related to the diameter d of the cylinder by
A
F \(\alpha\) d\(^2\)
B
F \(\alpha\) d
C
F \(\alpha\) d\(^{-1}\)
D
F \(\alpha\) d\(^{-2}\)
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #59466)
Physics
WAEC / WASSCE 2020
Waves and Optics
Solution
Which of the following statements correctly explains why a total solar eclipse would be seen by people on only a small portion of the earth's surface? The
A
moon is larger in diameter than the earth
B
earth is larger in diameter than the sun
C
earth revolves around the sun
D
earth is larger in diameter than the moon.
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
A total solar eclipse happens when the Moon passes between the Earth and the Sun, blocking the Sun’s light. Because the Earth’s diameter is much larger than the Moon’s, the Moon’s shadow covers only a small area on Earth, so only people in the narrow “path of totality” see the Sun fully covered.
Source: Myschool Past Questions Archive (Record #59468)
Physics
WAEC / WASSCE 2020
Mechanics and Properties of Matter
Solution
Water waves have a wavelength of 3.6cm and speed of 18cms\(^{-1 }\) in deep water. If the waves enter shallow water with wavelength of 2.0cm, calculate the speed of the waves in the shallow water.
A
0.4cms\(^{-1}\)
B
2.5cms\(^{-1}\)
C
10.0cms\(^{-1}\)
D
10.8cms\(^{-1}\)
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Velocity = frequency x wavelength
v = 18cm/s, wavelength = 3.6cm, then F = 5hertz
therefore, the speed of the wave in the shallow water = 5 x 2 = 10cm/s
NOTE; as a general rule, the frequency of a wave remains constant while speed and wavelength change as it travels from one medium to another.
Source: Myschool Past Questions Archive (Record #59469)
Physics
WAEC / WASSCE 2020
Electricity and Magnetism
An a.c. generator can be converted to a d.c. electric motor by replacing the
A
slip rings with a split ring and connecting a battery
B
split ring with slip rings and connecting a battery
C
a.c. with d.c. source and connecting slip rings
D
a.c. with d.c. source and connecting split rings
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #59470)
Physics
WAEC / WASSCE 2020
Waves and Optics
A ray of light travels obliquely from a less dense medium to a denser medium. Which of the following statements is true about the light?
A
The wavelength of the light increases in the second medium
B
The speed of the light increases in the second medium
C
The light refracts towards the normal
D
There Is a change in the frequency of the light
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 #59472)
Physics
WAEC / WASSCE 2020
Mechanics and Properties of Matter
Solution
An electron of mass 9.1x 10\(^{-31}\) kg is travelling at a speed of 2.0 x 10\(^6\)ms\(^{-1}\). Calculate the associate wavelength of the electron. [h = 6.6. x 10\(^{-34}\) Js]
A
3.63 x10\(^{-10}\) m
B
3.63 x 10\(^{-8}\) m
C
3.63 x 10\(^{-7}\) m
D
6.89 x 10\(^{-4}\) m
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Using de Broglie wavelength formula: \(\lambda\) = \(\frac{h}{p}\)
P = momentum = mass x velocity = 9.1x 10\(^{-31}\) x 2.0 x 10\(^6\) = 1.82 \times 10\(^{ −24}\) kg m/s
\(\lambda\) = \(\frac{6.6. \times 10^{-34}}{1.82 \times 10^{ −24}}\) = 3.63 x 10\(^{-10}\) m
Source: Myschool Past Questions Archive (Record #59476)
Physics
WAEC / WASSCE 2020
Thermal Physics
Solution
Which of the following statements about the process of melting of a solid are true? The temperature of the solid will
I. remain steady until melting starts.
ll. keep rising until melting starts,
Ill remain steady as melting proceeds.
V, keep rising as melting proceeds.
A
I and llI only
B
IlI and IV only
C
Il and Ill only
D
ll and IV only
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
During change of state, there is no change in temperature, for a solid to change to liquid, heat must be supplied and it starts rising again after melting has taken place. therefore, the temperature rises before melting takes place remains steady during melting, and keeps rising after melting.
Source: Myschool Past Questions Archive (Record #59477)
Physics
WAEC / WASSCE 2020
Electricity and Magnetism
A diver steps off a diving platform that is 10m above the water. If there is no air resistance during the fall, there will be a decrease in the diver's
A
gravitational potential energy
B
total mechanical energy
C
kinetic energy
D
momentum
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #59479)
Physics
WAEC / WASSCE 2020
Mechanics and Properties of Matter
Which of the following actions would increase the electric force between two positively charged particles?
A
Decreasing the mass of the particles
B
Decreasing the distance between the particles
C
Increasing the assistance between the particles
D
Increasing the mass of the particles
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 #59480)
Physics
WAEC / WASSCE 2020
Heat Energy & Temperature
A luminous object is one that
A
gives off dim blue-green light only in the dark.
B
gives out light of its own
C
shines by reflected light only
D
glows only in the presence of light
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 #59481)
Physics
WAEC / WASSCE 2020
Heat Energy & Temperature
Which of the following units is not fundamental?
A
Metre
B
Kilogram
C
Joule
D
Candela
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 #59482)
Physics
WAEC / WASSCE 2020
Heat Energy & Temperature
The vacuum between the double walls of a thermos flask reduces heat loss through
A
conduction and radiation
B
convection and conduction
C
radiation only
D
conduction only
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 #59484)
Physics
WAEC / WASSCE 2020
Electricity and Magnetism
In photoelectric effect, the number of electrode emitted per second from a metallic surface is proportional to the
A
intensity of the incident radiation
B
frequency of the incident radiation
C
energy of the incident radiation
D
work function of the metal.
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #59485)
Physics
WAEC / WASSCE 2020
Electricity and Magnetism
Solution
When two cells of negligible internal resistances and equal e.m.f. denoted by E\(_1\) and E\(_2\) are connected in parallel, combined e.m.f. E is given by
A
E = E\(_1\) + E\(_2\)
B
\(\frac{1}{E} = \frac{1}{E_1} + \frac{1}{E_2}\)
C
E = E\(_1\) = E\(_2\)
D
E = \(\frac{E_1}{E_2}\)
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
If two cells of equal emf s are connected in parallel then the effective emf is equal to the emf of any one of the cells.
Source: Myschool Past Questions Archive (Record #59486)