Sound practice worksheet | Exercises Physics | Docsity - Free Printable

Let's solve the problems step by step:

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Problem 1:

The frequency of a musical note is increased. A student hearing the sound detects an increase in which property?

- Options:
- A. Loudness of the sound
- B. Pitch of the sound
- C. Speed of the sound wave
- D. Wavelength of the sound wave

Solution:
- The pitch of a sound is directly related to its frequency. When the frequency increases, the pitch also increases.
- Loudness depends on the amplitude of the sound wave.
- The speed of sound in a medium is constant and does not depend on frequency.
- Wavelength is inversely proportional to frequency (λ = v/f), so as frequency increases, wavelength decreases.

Answer: B. Pitch of the sound

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Problem 2:

A man holding a starting pistol stands 640 m away from a spectator. The spectator hears the sound of the starting pistol 2.0 s after seeing the flash from the pistol. Using this information, what is the speed of sound in air?

- Given:
- Distance between the pistol and spectator = 640 m
- Time taken for sound to reach the spectator = 2.0 s

Solution:
- Speed of sound \( v \) can be calculated using the formula:
\[
v = \frac{\text{Distance}}{\text{Time}}
\]
Substituting the given values:
\[
v = \frac{640 \, \text{m}}{2.0 \, \text{s}} = 320 \, \text{m/s}
\]

Answer: B. 320 m/s

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Problem 3:

The diagrams represent two sound waves. The scales in the two diagrams are the same. Which statement describes the waves?

- Diagrams:
- Sound wave 1: Larger amplitude, longer wavelength
- Sound wave 2: Smaller amplitude, shorter wavelength

Solution:
- Loudness is determined by the amplitude of the wave. Since sound wave 1 has a larger amplitude, it is louder.
- Pitch is determined by the frequency (or wavelength). Since sound wave 1 has a longer wavelength, it has a lower frequency and thus a lower pitch.
- Therefore, the waves have different loudness and different pitch.

Answer: A. The waves have different loudness and different pitch.

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Problem 4:

What is the approximate range of audible sound frequencies for a human with good hearing?

- Options:
- A. From 20 Hz to 2000 Hz
- B. From 20 Hz to 20,000 Hz
- C. From 200 Hz to 20,000 Hz
- D. From 200 Hz to 200,000 Hz

Solution:
- The normal range of audible frequencies for humans is approximately 20 Hz to 20,000 Hz.

Answer: B. From 20 Hz to 20,000 Hz

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Problem 5:

A sound wave is traveling through water. What is a possible speed for the wave?

- Options:
- A. 150 m/s
- B. 300 m/s
- C. 1500 m/s
- D. 5000 m/s

Solution:
- The speed of sound in water is approximately 1500 m/s. This is much faster than in air but slower than in solids.

Answer: C. 1500 m/s

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Problem 6:

A pulse of sound is produced at the bottom of a boat. The sound travels through the water and is reflected from the sea-bed. The sound reaches the boat again after 1.3 s. The sea-bed is 1000 m below the boat. Using this information, what is the speed of sound in the water?

- Given:
- Total time for round trip = 1.3 s
- Distance to sea-bed = 1000 m

Solution:
- The total distance traveled by the sound wave is twice the depth of the sea-bed:
\[
\text{Total distance} = 2 \times 1000 \, \text{m} = 2000 \, \text{m}
\]
- Speed of sound \( v \) is given by:
\[
v = \frac{\text{Total distance}}{\text{Total time}} = \frac{2000 \, \text{m}}{1.3 \, \text{s}} \approx 1538 \, \text{m/s}
\]

Answer: C. 1538 m/s

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Problem 7:

A student stands a few hundred metres away from a wall and shouts. He hears a faint echo. Which statement is correct?

- Options:
- A. The sound waves returning are quiet because they have a reduced frequency.
- B. The sound waves returning are quiet because they have a reduced wavelength.
- C. The sound waves returning to the student are longitudinal.
- D. The sound waves returning to the student are transverse.

Solution:
- Sound waves are longitudinal waves, not transverse waves.
- The faintness of the echo is due to energy loss during reflection and propagation, not changes in frequency or wavelength.

Answer: C. The sound waves returning to the student are longitudinal.

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Problem 8:

Which statement about ultrasound is correct?

- Options:
- A. It is produced by a rapidly vibrating source.
- B. It is uncomfortable to human ears.
- C. Its frequency must be greater than 300 kHz.
- D. It travels the fastest in a vacuum.

Solution:
- Ultrasound is produced by a rapidly vibrating source with frequencies above the human hearing range (above 20 kHz).
- Ultrasound is generally not uncomfortable to human ears unless it is very intense.
- The frequency of ultrasound is typically above 20 kHz, not 300 kHz.
- Sound cannot travel in a vacuum.

Answer: A. It is produced by a rapidly vibrating source.

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Problem 9:

Which statement about sound waves is correct?

- Options:
- A. They are able to travel through a vacuum.
- B. They are able to travel through solids.
- C. They are transverse waves.
- D. They travel at the same speed in all substances.

Solution:
- Sound waves cannot travel through a vacuum.
- Sound waves can travel through solids, liquids, and gases.
- Sound waves are longitudinal waves, not transverse waves.
- The speed of sound varies depending on the medium (e.g., faster in solids than in gases).

Answer: B. They are able to travel through solids.

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Problem 10:

Both the amplitude and the frequency of a sound wave decrease. What happens to the sound heard?

- Options:
- A. The sound is louder and has a higher pitch.
- B. The sound is louder and has a lower pitch.
- C. The sound is quieter and has a higher pitch.
- D. The sound is quieter and has a lower pitch.

Solution:
- Amplitude determines loudness. If amplitude decreases, the sound becomes quieter.
- Frequency determines pitch. If frequency decreases, the pitch becomes lower.

Answer: D. The sound is quieter and has a lower pitch.

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Final Answers:

1. B. Pitch of the sound
2. B. 320 m/s
3. A. The waves have different loudness and different pitch.
4. B. From 20 Hz to 20,000 Hz
5. C. 1500 m/s
6. C. 1538 m/s
7. C. The sound waves returning to the student are longitudinal.
8. A. It is produced by a rapidly vibrating source.
9. B. They are able to travel through solids.
10. D. The sound is quieter and has a lower pitch.

\boxed{B, B, A, B, C, C, C, A, B, D}