Waec Physics 1991 Past Questions and Answers

Question 36:

• WAEC 1991

The sound from a bell in an enclosed jar gradually faints away while the jar is being evacuated. Which of the following explains this observation?

A. The pressue is reduced
B. The sound waves are pumped out
C. The waves are absorbed in the inner walls
D. There is no more material medium
E. The air is disturbed

Question 37:

• WAEC 1991

Which of the following statements is true of the diagram shown above?

A. The two point, A and B are in phase
B. Distance AB is halgf the wavelength of the wave
C. AC and BD are the amplitude of the wave
D. The two points A and B represents the wave crests
E. The wave has four crests

Question 38:

• WAEC 1991

A man standing 300m away from the wall sounds a whistle. The echo from the wall reaches him 1.8sec. later, calculate the velocity of sound in air

A. 540.0ms^-1
B. 333.3ms^-1
C. 270.0ms^-1
D. 166.7ms^-1
E. 83.3ms^-1

Question 39:

• WAEC 1991

In which of the following is a stationary wave produced? i. A vibrating turning fork held near the end of a resonance tube closed at one end. ii. A string tightly stretched between two points and plucked at its middle. iii. The tuning fork vibrating in air

A. I only
B. Ii only
C. I and ii only
D. Ii and iii only
E. I, ii and iii

Question 40:

• WAEC 1991

A particle of charge q and mass m moving with a velocity v enters a uniform magnetic field b in the direction of the field. The force on the particle is

A. QvB
B. MqvB/m
C. MvB/q
D. O