# Homework Help: Speed of a moving observer toward stationary source (sound frequency)

1. Apr 29, 2010

### rechitzy

1. The problem statement, all variables and given/known data

A stationary whistle emits a sound of 190 Hz. If a car hears the whistle with a frequency of 198 Hz, how fast was it moving (in m/s)? Use 340 m/s for the sound velocity

2. Relevant equations

f'=(1+Vo/V)f ======>>>> equation for the observer moving toward stationary source.

3. The attempt at a solution

f'=(1+Vo/V)f

198=(1+Vo/340)190

2. Apr 29, 2010

### nickjer

3. Apr 29, 2010

### rechitzy

i got 353.3157

4. Apr 29, 2010

### nickjer

Well, then you made a mistake in your math. I believe your equation is right, but you seem to be messing up when solving the algebra. Your velocity should not be that fast.

5. Apr 29, 2010

### rechitzy

ok i believe i did the 198/190 times 340 -1 is that right?

6. Apr 29, 2010

### vela

Staff Emeritus
No, it's not.

7. Apr 29, 2010

### rechitzy

ok i got a different answer now 14.3157 is this one right?

8. Apr 29, 2010