# Waves and sound

## Homework Statement

a)a stationary railroad whistle is sounded. An echo is heard 4.0 seconds later by a train's engineer. If the speed of sound is 343 m/s, how far away is the reflecting surface?
b) If the temperature of the air increased, how would this change your answer?

d=rt
x=xt/2

## The Attempt at a Solution

I got part a right. x=(343*4)/2 =686 because the sound has to travel twice
I do not know part b

berkeman
Mentor

## Homework Statement

a)a stationary railroad whistle is sounded. An echo is heard 4.0 seconds later by a train's engineer. If the speed of sound is 343 m/s, how far away is the reflecting surface?
b) If the temperature of the air increased, how would this change your answer?

d=rt
x=xt/2

## The Attempt at a Solution

I got part a right. x=(343*4)/2 =686 because the sound has to travel twice
I do not know part b
Welcome to the PF.

How does the speed of sound in air change with a change in air temperature?

Welcome to the PF.

How does the speed of sound in air change with a change in air temperature?
Higher the temperature faster the speed of sound. Thanks!

berkeman
Mentor
Higher the temperature faster the speed of sound. Thanks!
Really? That may be true, but it's counter-intuitive for me. Do you have a link to a reference that says that?