## Physics 2020 Past Question | WAEC

Study the following past questions and answers for JAMBWAEC  NECO and Post-JAMB. Get prepared with official past questions and answers for upcoming examinations.

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

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

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

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

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

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

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

23. Which of the current-voltage characteristics shown below is that exhibited an ohmic conductor?

• A. A
• B. B
• C. C
• D. D

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

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

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

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.

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

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

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

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