WAEC Physics 1992 past questions

Checked by the Skolra question team · Last updated 15 October 2026

Ten questions from the 1992 WAEC Physics paper, with answers and explanations. We hold 45 questions from this paper, and the Skolra app has all of them.

WAEC Physics 1992 questions and answers

1.A force of 20 N applied parallel to the surface of a horizontal table, is just sufficient to make a block of mass 4kg move on the table. Calculate the coefficient of friction between the block and the table. (g = 10ms²)
1. A
  0.2
2. B
  0.5
  Correct
3. C
  2.0
4. D
  5.0
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Answer: B
The coefficient of friction μ is given by:
μ = F / N = F / (mg)
where F = 20 N (friction force), m = 4 kg, g = 10 m s⁻²:
N = mg = 4 × 10 = 40 N
μ = 20 / 40 = 0.5
2.As an object is moved close to the focus of a converging lens from infinity its image I. moves closer to the lens II. moves away from the lens. III. Remains the same size. IV becomes smaller. Which of the statements above is/are correct?
1. A
  II and III
2. B
  I only
3. C
  I and IV
4. D
  II only
  Correct
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Answer: D
Using the lens formula 1/f = 1/u + 1/v, as an object moves from infinity toward the focus (u decreases from ∞ to f):
Image position: When u = ∞, v = f (image at focus). As u decreases toward f, v increases toward infinity. So the image moves away from the lens — statement II is correct; I is incorrect.
Image size: Magnification = v/u increases as the object approaches the focus (v → ∞, u → f). The image becomes larger, not smaller. So III and IV are both incorrect.
3.Which of the following has the same unit as the moment of a force?
1. A
  Pressure
2. B
  Work
  Correct
3. C
  Impulse
4. D
  Power
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Answer: B
Moment of a force = Force × perpendicular distance = N × m = N·m (Joule)
Work done = Force × displacement = N × m = N·m (Joule)
Both moment of a force and work have the SI unit of Joule (J) or N·m.
Power = J s⁻¹ (Watt); Pressure = N m⁻²; Impulse = N·s — none of these match.
4.A metal of mass 1.5 kg was heated from 27°C to 47°C in 4 minutes by a boiling ring of 75 W rating. Calculate the specific heat capacity of the metal, (Neglect heat losses to the surrounding)
1. A
  600 J kg⁻¹ K⁻¹
  Correct
2. B
  1200 J kg⁻¹ K⁻¹
3. C
  900 J kg⁻¹ K⁻¹
4. D
  300 J kg⁻¹ K⁻¹
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Answer: A
Energy supplied by the boiling ring:
Q = P × t = 75 W × (4 × 60 s) = 75 × 240 = 18 000 J
Using Q = mcΔT:
18 000 = 1.5 × c × (47 − 27) = 1.5 × c × 20 = 30c
c = 18 000 / 30 = 600 J kg⁻¹ K⁻¹
5.Calculate the length of a constantan wire of cross- sectional area 4 π x 10-8m² and resistivity 1.1 x 10-6 Ω m required to construct a standard resistor of resistance 21 Ω. [Take π = 22/7]
1. A
  9.6 m
2. B
  4.8 m
3. C
  1.2 m
4. D
  2.4 m
  Correct
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Answer: D
Using the resistance formula R = ρL/A, rearrange to find length:
L = RA/ρ
A = 4π × 10⁻⁸ m² = 4 × (22/7) × 10⁻⁸ = 88/7 × 10⁻⁸ m²
L = [21 × (88/7) × 10⁻⁸] / (1.1 × 10⁻⁶)
L = [21 × 88/7] / 1.1 × 10⁻²
L = [264] / 1.1 × 10⁻² = 240 × 10⁻² = 2.4 m
6.Which of the following radiations have the highest frequency?
1. A
  Gamma rays
  Correct
2. B
  Ultraviolet rays
3. C
  X-rays
4. D
  Infrared rays
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Answer: A
The electromagnetic spectrum, arranged from lowest to highest frequency, is: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays.
Gamma rays have the highest frequency (and therefore the shortest wavelength and highest energy) of all electromagnetic radiations. The relationship is given by E = hf, where E is energy, h is Planck's constant, and f is frequency.
7.A ray of light strikes a plane mirror at an angle of incidence i. Determine in terms of i the angle of deviation of the ray after reflection from the mirror.
1. A
  i
2. B
  2i
3. C
  (90° − i)
4. D
  (180° − 2i)
  Correct
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Answer: D
By the law of reflection, the angle of reflection equals the angle of incidence = i.
The angle between the incident ray and the reflected ray = 2i.
The angle of deviation is the angle between the original direction of travel and the final direction after reflection:
Deviation = 180° − 2i
Check: when i = 0° (normal incidence), deviation = 180° (ray reverses direction). When i = 90° (grazing), deviation = 0°.
8.Which of the following statements is correct about cathode rays? They are fast moving
1. A
  electrons
  Correct
2. B
  protons
3. C
  neutrons
4. D
  positrons
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Answer: A
Cathode rays were identified by J.J. Thomson as streams of electrons. Key properties of cathode rays:
- They are fast moving electrons emitted from the cathode.
- They travel in straight lines and carry a negative charge.
- They are deflected by both electric and magnetic fields.
- They cause fluorescence when they strike certain materials.
The mass-to-charge ratio (m/e) measured by Thomson confirmed they are electrons.
9.An element whose half-life is 3 years has N atoms. How many atoms would have decayed after 9 years
1. A
  3N/4
2. B
  N/4
3. C
  7N/8
  Correct
4. D
  N/2
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Answer: C
Half-life = 3 years, total time = 9 years.
Number of half-lives elapsed = 9/3 = 3 half-lives.
Remaining atoms after 3 half-lives: N_remaining = N × (½)³ = N/8
Atoms that have decayed = N − N/8 = 7N/8
10.A barometer can be used in determining the I. height of a mountain II. depth of a mine III. dew point. Which of the following is/are correct?
1. A
  I and II only
  Correct
2. B
  I, II and III
3. C
  I only
4. D
  II only
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Answer: A
A barometer measures atmospheric pressure, which varies with altitude.
I. Correct — Atmospheric pressure decreases with increasing altitude, so a barometer can be used to estimate the height of a mountain.
II. Correct — Pressure increases below ground level (in a mine), so a barometer can determine depth.
III. Incorrect — Dew point is determined by a hygrometer or psychrometer, not a barometer. A barometer measures pressure, not humidity.

The questions come from past JAMB, WAEC and NECO papers. We use software to help write the answer options and explanations, and every answer is checked twice before it goes on the site. How we check

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WAEC Physics 1992 past questions

WAEC Physics 1992 questions and answers

Practise all 45 questions we hold from the 1992 paper, on a timed CBT screen

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