Speed of Sound - UNSOLVED PRACTICE SET

Q7. Why does sound travel faster in solids than in liquids, and faster in liquids than in gases? Explain in terms of the arrangement of particles.

Q8. How does temperature affect the speed of sound in air? Explain with a reason. Does humidity affect the speed of sound?

Q9. During a cricket match in Chennai, a fielder hears the sound of the ball being hit 0.2 seconds after he sees it. If the speed of sound is 340 m/s, how far is the fielder from the batsman?

Q10. Why do we see lightning before we hear thunder, even though both are produced at the same instant? Use approximate speeds to explain. 

Q11. Give the approximate speeds of sound in air, water, and iron. What pattern do you notice? Explain why this pattern exists using the concept of intermolecular forces.

Q12. A boy places his ear on a long metal railway track. His friend taps the track with a hammer 1 km away. The boy hears two sounds — one through the track and one through the air. Explain why he hears two separate sounds and which he hears first.

Q13. Explain in detail the factors that affect the speed of sound. Your answer must cover:
(a) the effect of the nature of the medium (solid, liquid, gas) with approximate values,
(b) the effect of temperature on speed in air (speed increases by about 0.6 m/s per °C rise),
(c) the effect of humidity — does moist air carry sound faster or slower than dry air? Explain.
(d) does the frequency or amplitude of sound affect its speed?
(e) why ancient Indian hunters would press their ears to the ground to detect approaching horses — explain using speed of sound in solids.

Q14. In the mountains of Himachal Pradesh, a tourist hears the echo of her own voice from a cliff.
(a) Explain the phenomenon of echo (you will study it in detail later — just use what you know about reflection of sound).
(b) She hears the echo 3 seconds after she shouts. The speed of sound is 340 m/s. Calculate the distance of the cliff from her.
(c) If she moves 170 m closer to the cliff and shouts again, after how many seconds will she hear the echo?
(d) What is the minimum time gap required to hear a distinct echo, and what does this tell us about the minimum distance needed? 

Q15. Compare the speed of sound in different media through a structured analysis.
(a) State and explain the values of speed of sound in air (0°C), water, and steel.
(b) Explain why these values are so different using the concept of inter-particle bonding and spacing.
(c) Submarines use SONAR which relies on sound travelling through water. If a SONAR pulse travels at 1500 m/s, how long does it take to travel 3 km and return?
(d) A person speaks in a large empty hall — the sound seems to linger. Why? 

(e) On a hot summer afternoon in Rajasthan (temperature 45°C), is the speed of sound higher or lower than on a winter morning (5°C)? Estimate the difference using 0.6 m/s per °C. 

Q16. A thunderclap is heard 6 seconds after lightning is seen.
(a) Calculate the distance of the lightning if speed of sound in air = 340 m/s.
(b) Speed of light ≈ 3 × 10⁸ m/s. How long did the light take to travel the same distance?
(c) Why is the time taken by light considered negligible in this calculation?
(d) If the thunder was heard only 2 seconds later on another occasion, how much closer was the second lightning strike?

Q17. A SONAR device on a ship sends an ultrasonic pulse downward. The echo returns after 4 seconds. Speed of sound in seawater = 1500 m/s.
(a) Calculate the total distance travelled by the sound.
(b) Calculate the depth of the seabed below the ship.
(c) If the ship moves forward and the echo now returns in 3 seconds, what is the new depth?
(d) What does a shorter echo time tell us about the shape of the ocean floor here?

Q18. A teacher claps her hands at one end of a 340 m long school corridor.
(a) How long does the sound take to reach the other end? (speed of sound = 340 m/s)
(b) The sound reflects from the wall and returns. What is the total time for the round trip?
(c) If the corridor were made of polished stone instead of concrete, would the reflected sound be stronger or weaker? Explain.
(d) A metal rod of the same length (340 m) conducts sound at 5100 m/s. How much faster does sound travel in the rod compared to the corridor air?