http://www.ck12.org Chapter 11. Vibrations and Sound
through a vacuum. Number 1 above gave the velocity of sound for a temperature of 20◦Casvs= 343. 0 ms.
Answer:VVLs= 874 , 635. 57 → 8. 7 × 105. The velocity of light is indeed a good deal greater than the velocity of sound
in air. In fact, the velocity of light in vacuum is the greatest velocity that exists. No material object can travel at this
velocity! We will discuss these ideas in Chapter 22 (The Special Theory of Relativity).
- At the moment a lightning flash is seen, a person begins to count off seconds. If he hears the thunder after seven
seconds, approximately how far away from the person did the lightning flash originate?
Answer: We’ll assume that the sound travels at a velocity of 343 m/s. In seven seconds the sound has traveled
x=vt→x=
(
343 ms)
( 7 s) = 2401 → 2400 m.- Sound travels about 1,500 m/s in water. A destroyer ship locates an enemy submarine using a sonar signal which
takes a 4.3 s to travel to, reflect, and return to the destroyer. How far is the sub from the destroyer?
Answer: The time for the signal to reach the sub is half of the total time of travel,→^4.^32 s= 2. 15 → 2. 2 s. Using
x=vt→x=
(
1 , 500 ms)
( 2. 15 s) = 3225 → 3200 mor 3.2 km.