WAEC Physics 1989 past questions

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

Ten questions from the 1989 WAEC Physics paper, with answers and explanations. We hold 32 questions from this paper, and the Skolra app has all of them.

WAEC Physics 1989 questions and answers

1.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.
1. A
  2600 m
2. B
  200 m
  Correct
3. C
  1300 m
4. D
  100 m
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Answer: B
The depth of each reflecting layer is found using d = vt / 2.
Layer 1: d₁ = (2000 × 1.2) / 2 = 1200 m
Layer 2: d₂ = (2000 × 1.4) / 2 = 1400 m
Distance between the two layers = 1400 − 1200 = 200 m.
2.The distance between a node and an anti-node for a transverse wave is equal to
1. A
  λ/8
2. B
  λ
3. C
  λ/2
4. D
  λ/4
  Correct
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Answer: D
In a standing wave, nodes and antinodes alternate along the wave.
One complete wavelength λ contains two nodes and two antinodes, arranged: node → antinode → node → antinode.
The distance from a node to the nearest antinode is therefore λ/4.
3.Which of the following instruments can be used to compare the relative magnitude of similar charges on two given bodies?
1. A
  Voltmeter
2. B
  Ammeter
3. C
  Electroscope
  Correct
4. D
  Galvanometer
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Answer: C
A gold leaf electroscope detects and compares static electric charges.
When a charged body is brought near, the gold leaves diverge; the greater the charge, the larger the divergence. By comparing the leaf deflections for two bodies, the relative magnitude of their charges can be assessed.
An ammeter and galvanometer measure current (charge flow), not static charge; a voltmeter measures potential difference.
4.A thermometer has its stem marked in millimeter instead of degree Celsius. The lower fixed point is 30mm and the upper is 180mm. Calculate the temperature in degree celsius when the thermometer reads 45mm.
1. A
  30°C
2. B
  15°C
3. C
  20°C
4. D
  10°C
  Correct
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Answer: D
Using the thermometer scale formula:
θ = (L − L₀) / (L₁₀₀ − L₀) × 100°C
where L₀ = 30 mm (lower fixed point, 0°C), L₁₀₀ = 180 mm (upper fixed point, 100°C), and L = 45 mm (current reading).
θ = (45 − 30) / (180 − 30) × 100 = 15/150 × 100 = 10°C
5.An engine raises 1000kg of water through a height of 60m in 20s. What is the power of the engine? (Take g = 10ms^-2>).
1. A
  10 kW
2. B
  30 kW
  Correct
3. C
  20 kW
4. D
  40 kW
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Answer: B
Power is the rate of doing work:
P = W/t = mgh/t
P = (1000 × 10 × 60) / 20 = 600 000 / 20 = 30 000 W = 30 kW
6.The image in a pine-hole camera is always
1. A
  Real and erect
2. B
  Real and inverted
  Correct
3. C
  Virtual and diminished
4. D
  Virtual and erect
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Answer: B
In a pinhole camera, light from an object passes through a tiny hole and forms a real image on the screen opposite (real because the rays actually converge there). The image is always inverted (upside down and laterally reversed) because rays from the top of the object travel downward through the hole to reach the bottom of the screen, and vice versa.
The image may be smaller, equal to, or larger than the object depending on the distances involved, but it is always real and inverted.
7.Water in an open container boils at a lower temperature when heated at the top of a mountain than at sea-level because at the top of a mountain the
1. A
  atmospheric pressure is lower
  Correct
2. B
  altitude increases the specific heat capacity of water
3. C
  humidity of the air is lower
4. D
  temperature of the atmosphere is lower
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Answer: A
The boiling point of a liquid is the temperature at which its saturated vapour pressure equals the external (atmospheric) pressure.
At the top of a mountain, the atmospheric pressure is lower than at sea level. Water therefore reaches a vapour pressure equal to the reduced atmospheric pressure at a lower temperature, so it boils at a lower temperature.
8.
A block of ice at its melting point is left on a table in the atmosphere and observed to melt gradually. Which of the following statements is true about the melting process?
1. A
  The temperature of the ice remains constant throughout the melting process
  Correct
2. B
  The temperature of the ice rises gradually as it melts
3. C
  The temperature of the ice rises then falls to 0°C
4. D
  The temperature of the ice falls as it absorbs heat
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Answer: A
When a substance melts at its melting point, the heat energy supplied (latent heat of fusion) is used entirely to break the intermolecular bonds and change the state from solid to liquid. No temperature rise occurs during this phase change.
The ice absorbs latent heat from the surrounding atmosphere, yet its temperature stays at 0°C until all the ice has melted. This is a characteristic of all pure-substance phase transitions.
9.A stone tied to a string is made to revolve in a horizontal circle of radius 4m with an angular speed of 2 rad per sec. With what tangential velocity will the stone move off the circle if the string is cut?
1. A
  4 ms⁻¹
2. B
  8 ms⁻¹
  Correct
3. C
  6 ms⁻¹
4. D
  2 ms⁻¹
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Answer: B
For a body moving in a circle, the tangential (linear) speed is related to the angular speed by:
v = ωr
where ω = 2 rad s⁻¹ and r = 4 m.
v = 2 × 4 = 8 ms⁻¹
When the string is cut, the centripetal force vanishes and the stone flies off tangentially at this speed.
10.What is the gravitational potential due to a molecule of mass, m and at a distance, r from it? (G = gravitational constant).
1. A
  -Gm / r
  Correct
2. B
  Gm / r
3. C
  -Gm / r²
4. D
  Gm / r²
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Answer: A
Gravitational potential at a distance r from a mass m is defined as the work done per unit mass in bringing a test mass from infinity to that point.
The formula is: V = −Gm / r
The negative sign indicates that the gravitational field is attractive, so the potential is always negative relative to infinity.

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 1989 past questions

WAEC Physics 1989 questions and answers

Practise all 32 questions we hold from the 1989 paper, on a timed CBT screen

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