WAEC Physics 2011 past questions
Ten questions from the 2011 WAEC Physics paper, with answers and explanations. We hold 51 questions from this paper, and the Skolra app has all of them.
WAEC Physics 2011 questions and answers
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1.Nuclear fusion is not used as a source of energy because
- Athe extremely high temperature required to initiate fusion is difficult to achieve and sustain on EarthCorrect
- Bfusion fuels such as hydrogen isotopes are very scarce
- Cthe process releases too little energy to be economically viable
- Dfusion produces large amounts of long-lived radioactive waste
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Answer: A
Nuclear fusion requires temperatures of the order of 10⁷ to 10⁸ K (tens of millions to hundreds of millions of degrees Celsius) to overcome the electrostatic repulsion between positively charged nuclei. Achieving and sustaining such extreme temperatures in a controlled manner on Earth is the principal technological barrier to using fusion as a practical energy source.
- A
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2.A uniform metre rule is balanced on a fulcrum placed at the 35cm mark by suspending a mass of 120g at the 10cm mark. Calculate the mass of the metre rule.
- A150 g
- B240 g
- C100 g
- D200 gCorrect
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Answer: D
For a uniform metre rule, the centre of mass is at the 50 cm mark. Taking moments about the fulcrum at the 35 cm mark:
Anticlockwise moment = Clockwise moment
120 g × (35 − 10) cm = M × (50 − 35) cm
120 × 25 = M × 15
3000 = 15M
M = 3000 ÷ 15 = 200 g - A
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3.The radius of a wheel is 30.0 cm and that of its axle is 6.0cm. Calculate the effort required to lift a load of 120.0N using this machine. Assuming 100% efficiency
- A40.0 N
- B30.0 N
- C24.0 NCorrect
- D20.0 N
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Answer: C
For a wheel and axle: Velocity Ratio (VR) = R_wheel / R_axle = 30.0 / 6.0 = 5
At 100% efficiency, Mechanical Advantage (MA) = VR = 5
Effort = Load / MA = 120.0 / 5 = 24.0 N - A
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4.The unit of capacitance is
- AWeber (Wb)
- BFarad (F)Correct
- CHenry (H)
- DSiemens (S)
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Answer: B
The SI unit of capacitance is the Farad (F), named after Michael Faraday. One farad equals one coulomb per volt (C/V). In practice, most capacitors have capacitances measured in microfarads (μF) or picofarads (pF). Henry (H) is the unit of inductance; Weber (Wb) is the unit of magnetic flux; Siemens (S) is the unit of electrical conductance.
- A
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5.The change in mass of fuel during a nuclear reaction is 2.0 x 10-27 kg. Calculate the amount of energy released. (Speed of light = 2.0 x 108ms-1)
- A8.0 × 10⁻¹⁸ J
- B4.0 × 10⁻¹¹ J
- C4.0 × 10⁻¹⁸ J
- D8.0 × 10⁻¹¹ JCorrect
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Answer: D
Using Einstein's mass-energy equivalence:
E = mc²where m = 2.0 × 10⁻²⁷ kg and c = 2.0 × 10⁸ ms⁻¹ (as given in the question)
E = 2.0 × 10⁻²⁷ × (2.0 × 10⁸)²
E = 2.0 × 10⁻²⁷ × 4.0 × 10¹⁶
E = 8.0 × 10⁻¹¹ J - A
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6.A ray undergoes a minimum deviation at 40o when it is incident on equilateral triangular glass prism. Calculate the refractive index of the prism
- A1.20
- B1.53Correct
- C1.41
- D1.73
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Answer: B
For a prism of apex angle A at minimum deviation D_m, the refractive index is:
n = sin[(A + D_m)/2] / sin(A/2)
For an equilateral prism, A = 60°; given D_m = 40°:
n = sin[(60° + 40°)/2] / sin(60°/2) = sin(50°) / sin(30°)
n = 0.7660 / 0.5000 = 1.53 - A
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7.In the absence of gravitational force, the weight of the body is
- Aequal to its mass
- BzeroCorrect
- Cequal to the normal reaction on it
- Dat its maximum value
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Answer: B
Weight is defined as W = mg, where g is the gravitational field strength. In the absence of gravitational force, g = 0, therefore W = m × 0 = 0. The body is said to be weightless. Note that the mass of the body remains unchanged — only the weight becomes zero.
- A
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8.The correct relationship between "G" and "g" in a gravitational field is given by the equation (Where the symbols have their usual meanings)
- AG = gR/M
- Bg = GM/R
- Cg = GM/R²Correct
- Dg = G/(MR²)
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Answer: C
The gravitational field strength g at the surface of a planet of mass M and radius R is derived by equating Newton's second law with Newton's law of gravitation:
mg = GMm/R² (where m is the mass of the object on the surface)
Dividing both sides by m: g = GM/R²
This shows g is directly proportional to M and inversely proportional to R². G is the universal gravitational constant (6.674 × 10⁻¹¹ N m² kg⁻²). - A
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9.The speed of light in a certain medium is V while its speed in a vacuum is C. The absolute refractive index of the medium is
- AC/VCorrect
- B(C − V)/V
- CV/C
- DC × V
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Answer: A
The absolute refractive index of a medium is defined as the ratio of the speed of light in a vacuum to the speed of light in that medium:
n = c / v
where c is the speed of light in vacuum (~3 × 10⁸ ms⁻¹) and v is the speed of light in the medium. Since light always slows down when entering a medium (n ≥ 1), n = C/V is always greater than or equal to 1. - A
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10.A wire of length 30cm is moved with a speed of 2ms-1 at right angles to a magnetic field of flux density 0.4T. calculate the emf induced in the wire
- A0.48 V
- B0.12 V
- C1.20 V
- D0.24 VCorrect
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Answer: D
The EMF induced in a straight conductor moving through a magnetic field is:
EMF = BLv
where B = flux density, L = length of conductor, v = velocity.L = 30 cm = 0.30 m
EMF = 0.4 T × 0.30 m × 2 ms⁻¹ = 0.24 V - 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 51 questions we hold from the 2011 paper, on a timed CBT screen
Every question has the answer and an explanation, in the Skolra app.