WAEC Physics 1997 past questions
Ten questions from the 1997 WAEC Physics paper, with answers and explanations. We hold 43 questions from this paper, and the Skolra app has all of them.
WAEC Physics 1997 questions and answers
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1.The half-life of a radioactive material is 6hrs. What quantity of 1kg of the material would decay in 24 hours?
- A15/16 kgCorrect
- B1/16 kg
- C3/4 kg
- D1/4 kg
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Answer: A
Number of half-lives in 24 hours: n = 24 / 6 = 4
Amount remaining = (1/2)4 × 1 kg = 1/16 kg
Amount decayed = 1 − 1/16 = 15/16 kg
- A
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2.The ratio of tensile stress to tensile strain is known as
- Amodulus of rigidity
- BYoung's modulusCorrect
- Cbulk modulus
- Dmodulus of elasticity
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Answer: B
Young's modulus (E) is defined as the ratio of tensile stress to tensile strain within the elastic limit of a material:
E = (tensile stress) / (tensile strain) = (F/A) / (ΔL/L)
It measures the stiffness of a solid material along an axis.
- A
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3.A solid material of volume 100 cm^-3 is heated through a temperature difference of 40°C. Calculate the increase in the volume of the material if its linear expansitivity is 2 x 10^-6 K^-1
- A9.6 × 10⁻² cm³
- B2.4 × 10⁻² cm³Correct
- C4.8 × 10⁻² cm³
- D8.0 × 10⁻³ cm³
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Answer: B
The cubic (volumetric) expansivity γ = 3α:
γ = 3 × 2 × 10⁻⁶ = 6 × 10⁻⁶ K⁻¹
ΔV = γVΔT
ΔV = 6 × 10⁻⁶ × 100 × 40
ΔV = 2.4 × 10⁻² cm³ - A
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4.The invisible part of the spectrum of a white light consists of the following colors
- Aviolet and red
- Bultraviolet and infraredCorrect
- Cgamma rays and X-rays
- Dblue and green
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Answer: B
When white light is dispersed into a spectrum, the visible range extends from red to violet (ROYGBIV).
Beyond the red end lies infrared radiation, and beyond the violet end lies ultraviolet radiation. Both are invisible to the human eye and represent the invisible extensions of the white light spectrum.
- A
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5.An object falls freely from a height of 25m onto the roof a building 5m high. Calculate the velocity with which the object strikes the roof (g=10 ms^-2)
- A15 m s⁻¹
- B25 m s⁻¹
- C20 m s⁻¹Correct
- D10 m s⁻¹
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Answer: C
The object falls from 25 m height onto a roof at 5 m height, so the effective fall distance is 25 − 5 = 20 m.
Using v² = u² + 2gs (u = 0, g = 10 m s⁻², s = 20 m):
v² = 0 + 2 × 10 × 20 = 400
v = 20 m s⁻¹ - A
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6.Which of the following is not true of the similarities between a camera and the human eye?
- ABoth have an aperture to control the amount of light entering
- BBoth form a real inverted image on a receiving surface
- CIn both, focusing is achieved by changing the curvature of the lensCorrect
- DBoth use a convex (converging) lens to form an image
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Answer: C
The camera focuses by moving the lens towards or away from the film, keeping the lens curvature fixed.
The human eye focuses (accommodation) by the ciliary muscles changing the curvature of the flexible crystalline lens.
Therefore, option C is not a true similarity — it describes only the eye's mechanism, not the camera's.
- A
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7.Which of the following explains why a thick glass cup cracks when boiling water is poured into it?
- Aboiling water has a lower density than cold water
- Bglass expands uniformly throughout its thickness when heated
- Cthe inner surface expands faster than the outer surface because glass is a poor conductor of heatCorrect
- Dglass has a very high specific heat capacity
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Answer: C
Glass is a poor conductor of heat. When boiling water is poured in, the inner surface heats up and expands rapidly while the outer surface remains relatively cool and unexpanded. This differential expansion creates internal stress that exceeds the tensile strength of the glass, causing it to crack.
- A
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8.Steel bars each of length 3m at 28°C are to be used for constructing a rail line. If the linear expansitivity of the steel is 1 x 10^-5 K^-1, what is the safety gap that must be left between the successive bars if the highest temperature expected is 40°C?
- A1.2 × 10⁻⁴ m
- B4.8 × 10⁻⁴ m
- C2.4 × 10⁻⁴ m
- D3.6 × 10⁻⁴ mCorrect
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Answer: D
The safety gap equals the thermal expansion of each bar:
ΔL = αLΔT
ΔL = 1 × 10⁻⁵ × 3 × (40 − 28)
ΔL = 1 × 10⁻⁵ × 3 × 12
ΔL = 3.6 × 10⁻⁴ m - A
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9.A missile weighing 400N on the earth surface is shot into the atmosphere to an altitude of 6.4 x 10^-6 m. Taking the earth as a sphere of radius 6.4 x 10^-6 m and assuming the inverse-square law of universal gravitation, what would be the weight of the missile at that altitude?
- A200 N
- B100 NCorrect
- C400 N
- D50 N
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Answer: B
By the inverse-square law of gravitation, if the altitude h equals the Earth's radius R, the distance from the Earth's centre becomes 2R.
W' = W × (R / (R + h))²
W' = 400 × (R / 2R)²
W' = 400 × (1/2)²
W' = 400 × 1/4
W' = 100 N - A
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10.The current in the primary coil of a transformer is 2.5A. If the coil has 50 turns and the secondary 250 turns, calculate the current in the secondary coil.
- A0.5 ACorrect
- B12.5 A
- C2.5 A
- D1.0 A
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Answer: A
For an ideal transformer, the ratio of currents is inversely proportional to the ratio of turns:
I₁N₁ = I₂N₂
I₂ = I₁ × (N₁/N₂) = 2.5 × (50/250) = 2.5 × 0.2 = 0.5 A
- A
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
Spotted a wrong answer? Tell us from the app or on the contact page and we check it.
Practise all 43 questions we hold from the 1997 paper, on a timed CBT screen
Every question has the answer and an explanation, in the Skolra app.