Physics 2020 Past Question | WAEC
31. Which of the following statements about the motion of a simple pendulum is true?
- A. It is a simple harmonic motion when the angle of displacement is large
- B. It passes the equilibrium position with minimum speed
- C. It possesses maximum kinetic energy at the extreme positions
- D. lt swings faster at the poles than at the equator
32. An electron of mass m and charge e moves in a circular path in a magnetic field of flux density B. How long does it take to complete one orbit?
- A. 2me/Bπ
- B. 2Bmeπ2B/meπ
- C. 2πm/Be
- D. Be/2πm
33. Which of the following statements about photoelectrons is correct?
- A. A faint green light produces photoelectrons with less kinetic energy than a bright red light
- B. A red light releases a smaller number of electrons than a green light
- C. A faint green light produces photoelectrons with greater kinetic energy than a bright red light
- D. A red light produces more photoelectrons than a green light
34. The sketched graph above illustrates the heating curve of a 0.02kg of water. Determine the approximate value of the specific latent heat of vapourization of water
- A. 2.25 x 106 J kg−1
- B. 4.17 x 103 J kg−1
- C. 2.00 x 103 J kg−1
- D. 1.00 x 103 J kg−1
35. In the hydraulic press, the force F applied is related to the diameter d of the cylinder by
- A. F α d2
- B. F α d
- C. F α d−1
- D. F α d−2
36. In an electric circuit, an inductor of inductance 0.5 H and resistance 50Ωis connected to an alternating current source of frequency 60 Hz. Calculate the impedance of the circuit.
- A. 50.0Ω
- B. 450.5 Ω
- C. 195.0 Ω
- D. 1950.1 Ω
37. Which of the following statements correctly explains why a total solar eclipse would be seen by people on only a small portion of the earth’s surface? The
- A. moon is larger in diameter than the earth
- B. earth is larger in diameter than the sun
- C. earth revolves around the sun
- D. earth is larger in diameter than the moon.
38. Water waves have a wavelength of 3.6cm and speed of 18cms−1in deep water. If the waves enter shallow water with wavelength of 2.0cm, calculate the speed of the waves in the shallow water.
- A. 0.4cms−1
- B. 2.5cms−1
- C. 10.0cms−1
- D. 10.8cms−1
39. An a.c. generator can be converted to a d.c. electric motor by replacing the
- A. slip rings with a split ring and connecting a battery
- B. split ring with slip rings and connecting a battery
- C. a.c. with d.c. source and connecting slip rings
- D. a.c. with d.c. source and connecting split rings
40. A ray of light travels obliquely from a less dense medium to a denser medium. Which of the following statements is true about the light?
- A. The wavelength of the light increases in the second medium
- B. The speed of the light increases in the second medium
- C. The light refracts towards the normal
- D. There Is a change in the frequency of the light
41. An electron of mass 9.1x 1031kg is travelling at a speed of 2.0 x 1066ms−1. Calculate the associate wavelength of the electron. [h = 6.6. x 1034Js]
- A. 3.63 x1010 m
- B. 3.63 x 10−8 m
- C. 3.63 x 10−7 m
- D. 6.89 x 10−4 m
42. Which of the following statements about the process of melting of a solid are true? The temperature of the solid will
- remain steady until melting starts.
- keep rising until melting starts,
Ill remain steady as melting proceeds.
V, keep rising as melting proceeds.
- A. II and llI only
- B. IlI and IV only
- C. I, Il and Ill only
- D. ll and IV only
43. A diver steps off a diving platform that is 10m above the water. If there is no air resistance during the fall, there will be a decrease in the diver’s
- A. gravitational potential energy
- B. total mechanical energy
- C. kinetic energy
- D. momentum
44. Which of the following actions would increase the electric force between two positively charged particles?
- A. Decreasing the mass of the particles
- B. Decreasing the distance between the particles
- C. Increasing the assistance between the particles D. Increasing the mass of the particles
45. A luminous object is one that
- A. gives off dim blue-green light only in the dark.
- B. gives out light of its own
- C. shines by reflected light only
- D. glows only in the presence of light