Physics 2020 Past Question | WAEC
16. A ray of light travelling from glass into ethyl alcohol is incident at the boundary at an angle of incidence 3o. Calculate the angle of refraction. [Refractive index of glass =1.5; refractive index of ethyl alcohol = 1.36]
- A. 27o
- B. 33.5o
- C. 51.7o
- D. 72.8o
Correct Option: Answer is C
17. A 60kg man stands on a weighing balance in an elevator. If the elevator accelerates upwards at 5ms−2, determine the reading of the scale. [g = 10ms−2]
- A. 300N
- B. 600N
- C. 800N
- D. 900N
Correct Option: Answer is D
18. The length of an iron bar is 100cm at 20°C. At what temperature will its length increase by 0.01%? [Linear expansivity of iron = 1.2 x 10−5°C]
- A. 48.0°C
- B. 38.0°C
- C. 28.3°C
- D. 23.0°C
Correct Option: Answer is C
19. A moving-coil galvanometer which gives a full-scale on deflection with 0.005A is converted to a voltmeter reading up to 5V using an external resistance of 975Ω. What is the resistance of the metre?
- A. 0.25Ω
- B. 2.50Ω
- C. 25.00Ω
- D. 250.00Ω
Correct Option: Answer is C
20. A beam consisting of α-particles. β-particles and γ-rays pass through a magnetic field at right angles to the direction of the field. Which of the following observations would be made about the αα-particles, β-particles, and γ-rays respectively?
- A. Deflected, deflected, deflected
- B. Deflected, deflected, not deflected
- C. Deflected, not deflected, deflected
- D. Not deflected, deflected, deflected
Correct Option: Answer is B
21. A parallel plate capacitor is charged and the charging battery is subsequently disconnected. lf the plates of the capacitor are moved farther apart by means of insulating handles, the
- A. capacitance would increase
- B. capacitance would decrease
- C. charge on the capacitor would increase
- D. charge on the capacitor would decrease
Correct Option: Answer is A
22. The velocity of sound in air at 15°C is 35400ms−1. Calculate the velocity at 47oC
- A. 790ms−1
- B. 602ms−1
- C. 358ms−1
- D. 322ms−1
Correct Option: Answer is C
23. Which of the current-voltage characteristics shown below is that exhibited an ohmic conductor?
- A. A
- B. B
- C. C
- D. D
Correct Option: Answer is B
24. A 500N box rests on a horizontal floor. A constant horizontal force is exerted on the box so that it moves through 8m. If the coefficient of kinetic friction between the floor and the box is 0.22, calculate the workdone on the box
- A. 880J
- B. 440J
- C. 400J
- D. 110J
Correct Option: Answer is C
25. The diagram illustrates a ball of mass m sliding down a plank inclined at an angle of 0 to the horizontal. The kinetic friction between the ball and the plank is F and acceleration of free fall is g. The normal force on the ball is?
- A. mgsin θ
- B. mgtan θ, mgcos θ
- C. mgcos θ
- D. mgcot θ
Correct Option: Answer is C
26. The diagram above illustrates a ball of mass m sliding down a plank inclined at an angle of 0 to the horizontal. The kinetic friction between the ball and the plank is F and the acceleration of free fall is g. The net force on the ball along the plank is?
- A. mgsin θ + F
- B. F – mgcos θ
- C. mgsin θ – F
- D. F + mgcos θ
Correct Option: Answer is C
27. What factors determine the frequency of a note emitted by a vibrating string?
- A. Amplitude of vibration, force constant of string and length of string
- B. Amplitude of vibration, force constant of string, and tension in string
- C. Mass per unit length of string, tension in string and length of string
- D. Force constant of string, tension in string, and length of string.
Correct Option: Answer is A
28. The magnitude of the force experienced by a charge of 1.6 x 10−8C in a uniform electric field of intensity 5 x 105NC−1is
- A. 3.2 x 10−14N
- B. 8.0 x 10−13N
- C. 8.0 x 10−3N
- D. 3.1 x 1013 N
Correct Option: Answer is B
29. A motorcycle starting from rest is uniformly accelerated such that its velocity in 10s is 72kmhr−1. What is its acceleration?
- A. 108ms2
- B. 86ms2
- C. 4ms2
- D. 2ms2
where u = o m/s, t = 10s,
v = 72kmhr−1 —> (72 X 1000) / 3600
: v = 20 m/s
Acceleration (a) = (v – u ) / t —> (20 – 0) / 10
: a = 2m/s2
30. The temperature of an object is raised by 120°C. The resulting increase in its absolute temperature is
- A. 50K
- B. 120 K
- C. 200K
- D. 393K