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Standing Waves and Resonance

Question 1

Which of these is a requirement for a standing wave to form?

  • A) Two identical waves moving in the same direction.
  • B) Two identical waves moving in the opposite direction.
  • C) Two waves with identical wavelengths but different frequencies.
  • D) One end of the wave must be free.

Answers and Explanations

Question 2

What is referred to as a node of a standing wave?

  • A) The point on the wave that always oscillates between the 2 extremes.
  • B) The point on the wave that never moves.
  • C) Points that are separated by a distance of λ4
  • D) A standing wave doesn't have nodes.

Answers and Explanations

Question 3

Which of these is true for a standing wave?

  • A) There is no progression of energy.
  • B) All points between 2 successive nodes are out of phase.
  • C) All points have the same amplitude.
  • D) All particles have the same frequency.

Answers and Explanations

Question 4

What is critical damping?

  • A) When an object tends to the equilibrium position slowly.
  • B) When an object returns to equilibrium quickly, but without crossing the equilibrium point.
  • C) All damping is critical.
  • D) When an object returns to equilibrium after 2-3 oscillations.

Answers and Explanations

Question 5

What is resonance?

  • A) When the driving frequency is equal to the reciprocal natural frequency we get the largest amplitude.
  • B) When the driving frequency is equal to the reciprocal natural frequency we get the smallest amplitude.
  • C) When the driving frequency is equal to the natural frequency we get the smallest amplitude.
  • D) When the driving frequency is equal to the natural frequency we get the largest amplitude.

Answers and Explanations

Question 6

In what way does damping affect resonance?

  • A) It reduces the maximum amplitude.
  • B) It reduces the resonant frequency.
  • C) It reduces both the maximum amplitude and the resonant frequency.
  • D) It increases the resonant frequency.

Answers and Explanations

Question 7

Which of the following statements about standing waves is correct?

  • A) All points on a standing wave have the same amplitude.
  • B) Standing waves are formed by the superposition of two waves traveling in opposite directions.
  • C) Standing waves transfer energy from one point to another.
  • D) All points on a standing wave are in phase.

Answers and Explanations

Question 8

For a standing wave on a string fixed at both ends, the distance between two adjacent nodes is 0.5m. What is the wavelength of the wave?

  • A) 0.5m
  • B) 1.0m
  • C) 1.5m
  • D) 2.0m

Answers and Explanations

Question 9

In a standing wave, what is the phase difference between two points that are one-quarter of a wavelength apart?

  • A) 0
  • B) 90
  • C) 180
  • D) 270

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Question 10

A pipe closed at one end has a length of 0.85m. If the speed of sound in air is 340m/s, what is the fundamental frequency of the standing wave in the pipe?

  • A) 100Hz
  • B) 200Hz
  • C) 300Hz
  • D) 400Hz

Answers and Explanations

Question 11

What happens to the amplitude of oscillation of a system at resonance when the driving frequency matches the natural frequency?

  • A) The amplitude is zero.
  • B) The amplitude remains constant.
  • C) The amplitude is maximum.
  • D) The amplitude increases indefinitely.

Answers and Explanations

Question 12

How does increasing the damping of a system affect the resonance curve?

  • A) The amplitude at resonance increases, and the resonant frequency shifts higher.
  • B) The amplitude at resonance decreases, and the resonant frequency shifts lower.
  • C) The amplitude at resonance decreases, but the resonant frequency remains the same.
  • D) The amplitude at resonance increases, but the resonant frequency remains the same.

Answers and Explanations

Question 13

A mass-spring system has a natural frequency of 5.0Hz. If an external driver oscillates at 5.0Hz, what is the amplitude of oscillation of the mass compared to when the driver frequency is 4.5Hz, assuming minimal damping?

  • A) The amplitude is the same at both frequencies.
  • B) The amplitude is greater when the driver frequency is 5.0Hz.
  • C) The amplitude is greater when the driver frequency is 4.5Hz
  • D) There is no oscillation at 4.5Hz.

Answers and Explanations

Question 14

A string fixed at both ends has a length of 1.2m. The speed of waves on the string is 240m/s. What is the frequency of the second harmonic?

  • A) 100Hz
  • B) 200Hz
  • C) 300Hz
  • D) 400Hz

Answers and Explanations