WAEC Physics 2019 past questions
Ten questions from the 2019 WAEC Physics paper, with answers and explanations. We hold 43 questions from this paper, and the Skolra app has all of them.
WAEC Physics 2019 questions and answers
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1.
In which of the followingmedia is the speed of sound the least?
- Amercury
- Bsteel
- Cwater
- DairCorrect
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Answer: D
The speed of sound depends on the medium's elasticity and density. The general order is:
Gases < Liquids < Solids
In air at room temperature, the speed of sound is approximately 340 m/s. In water it is about 1500 m/s, and in steel about 5000 m/s. Gases have the weakest intermolecular forces and lowest bulk modulus, giving the slowest speed.
- A
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2.
Which of the following materials does not serve as a safety device in electrical circuits?
- ARheostatCorrect
- BFuse wire
- CCircuit breaker
- DEarth wire
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Answer: A
A rheostat is a variable resistor used to control current in a circuit. It is not a safety device.
Safety devices in electrical circuits include the fuse wire (melts to break the circuit during overcurrent), the circuit breaker (trips automatically on fault), and the earth wire (provides a safe low-resistance path to earth in case of a fault). A rheostat only varies resistance and does not protect the circuit or user from electrical hazards.
- A
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3.
Which property of a wave remains constant when the wave travels from one medium into another?
- AFrequencyCorrect
- BAmplitude
- CSpeed
- DWavelength
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Answer: A
When a wave travels from one medium into another, its frequency remains constant.
This is because frequency is determined by the source of the wave and does not change with the medium. Using the wave equation v = fλ, when a wave enters a different medium, its speed (v) changes. Since frequency (f) is constant, the wavelength (λ) must change accordingly. Speed and wavelength both change; amplitude may also change at the boundary, but frequency is always invariant.
- A
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4.
A transverse pulse of frequency 9 Hz traves 4.5m in 0.6 s. Calculate the wavelength of the pulse.
- A0.83 mCorrect
- B0.67 m
- C1.50 m
- D1.20 m
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Answer: A
First calculate the wave speed:
v = distance / time = 4.5 m ÷ 0.6 s = 7.5 m/s
Then apply the wave equation:
v = fλ → λ = v/f = 7.5 ÷ 9 = 0.83 m
- A
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5.
Which of the following statements about a moving object is correct?
- Ait always has kinetic energyCorrect
- Bno net force acts on it
- Cit always has both kinetic and potential energy
- Dits acceleration is always zero
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Answer: A
A moving object has a non-zero velocity (v > 0), so it always possesses kinetic energy:
KE = ½mv²
Since both m and v² are positive, KE is always greater than zero for a moving object. Potential energy depends on position (not motion alone), and a net force may or may not act depending on the situation.
- A
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6.
The time rate of increase in velocity is called
- Avelocity
- Bmomentum
- CaccelerationCorrect
- Dimpulse
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Answer: C
Acceleration is defined as the rate of change of velocity with time:
a = Δv / Δt
When velocity increases over time, the time rate of that increase is the acceleration. Momentum is mass × velocity, impulse is force × time, and velocity is the rate of change of displacement — none of these is the rate of increase in velocity.
- A
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7.
Calculate the quantity of heat needed to change the temperature of 60g of ice at 0 °C to 80 °C.[specific latent heat of fusion of ice= 3.36 x 10 Jkg specific heatcapacity of water 4.2 x 10 J kg K]
- A3.36 × 10⁴ J
- B2.02 × 10⁴ J
- C6.05 × 10⁴ J
- D4.03 × 10⁴ JCorrect
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Answer: D
Two stages of heating are required:
Stage 1 — Melting ice at 0°C:
Q₁ = mL = 0.060 × 3.36 × 10⁵ = 20,160 J
Stage 2 — Heating water from 0°C to 80°C:
Q₂ = mcΔT = 0.060 × 4200 × 80 = 20,160 J
Total Q = Q₁ + Q₂ = 20,160 + 20,160 = 40,320 J ≈ 4.03 × 10⁴ J
- A
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8.
Which of the following waves is not mechanical?
- Awater waves
- Bsound waves
- Cseismic waves
- Dlight wavesCorrect
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Answer: D
Mechanical waves require a material medium to propagate — they transfer energy through particle-to-particle interaction. Sound waves, water waves, and seismic waves are all mechanical.
Light waves are electromagnetic waves — they consist of oscillating electric and magnetic fields and can travel through a complete vacuum, requiring no medium. This makes light a non-mechanical wave.
- A
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9.
A body of mass 2 kg is released from a point 100 m above the ground. Calculate its kinetic energy 80m from the point of release.
- A1600 JCorrect
- B3200 J
- C2000 J
- D800 J
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Answer: A
Using conservation of mechanical energy, the kinetic energy gained equals the gravitational potential energy lost over the 80 m fall:
KE = mgh
KE = 2 kg × 10 m s⁻² × 80 m
KE = 1600 J
(Taking g = 10 m s⁻²)
- A
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10.
A rectangular piece of ironmeasuring 4 cm by 3 cm at 20C is heated until its temperature increases by 100 C. Calculate the new areaof the metal.[Linear expansivity of iron is 1.2x 10K]
- A12.58 cm²
- B12.03 cm²Correct
- C11.97 cm²
- D12.29 cm²
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Answer: B
Using the formula for area expansion: A = A₀(1 + 2αΔT)
Given: Original dimensions = 4 cm × 3 cm, so A₀ = 12 cm²
α (linear expansivity) = 1.2 × 10⁻⁵ K⁻¹
ΔT = 100 KA = 12 × (1 + 2 × 1.2 × 10⁻⁵ × 100)
A = 12 × (1 + 2.4 × 10⁻³)
A = 12 × 1.0024
A = 12.0288 cm² ≈ 12.03 cm² - 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
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Practise all 43 questions we hold from the 2019 paper, on a timed CBT screen
Every question has the answer and an explanation, in the Skolra app.