An echo is heard from a building 0.721 s after you shout "hello." How many feet away is the building if the air temperature is 21.5°C?
1
Expert's answer
2019-04-11T09:35:20-0400
Let's first find the speed of sound at temperature 21.5°C from the formula:
c=MγRT,
here, c is the speed of sound at temperature 21.5°C, γ=1.402 is the adiabatic index of air, R=8.3145mol⋅KJ is the molar gas constant, T is the temperature in Kelvin and M=0.0289645molkg is the molar mass of air.
Then, we can find the distance from the building to the person from the formula:
c=TimeTotalDistance=t2s,
here, s is the distance traveled by the sound to the building (since the sound reflects back from the building to the person, the total distance traveled by the sound is doubled), t is the time.
Therefore, from this formula we can find the distance from the building to the person:
Comments
Leave a comment