# Homework Help: What frequency did you hear 3 seconds after police pass?

1. Mar 20, 2016

### ThePhysicsXV

1. The problem statement, all variables and given/known data
The police was headed to a felony and passed you so you stopped. What frequency did you hear 3 second after the police passed you?

2. Relevant equations
f=1/T
3. The attempt at a solution
f=1/3
f=.33Hz

Last edited by a moderator: Mar 20, 2016
2. Mar 20, 2016

### Staff: Mentor

No.

What is the frequency of the siren? Do you only hear it as it approaches (so Doppler shifted to a higher frequency than its no-movement frequency)? Or do you know what its non-moving base frequency is?

What is the equation for the Doppler shift in frequency versus relevant velocities of the source and listener? You are missing so much from this post. Please fix it...

3. Mar 20, 2016

### ThePhysicsXV

So what's the correct formula?

4. Mar 20, 2016

### ThePhysicsXV

Frequency of Siren is 988Hz

5. Mar 20, 2016

### Staff: Mentor

You are the student, so you must tell us that.

6. Mar 20, 2016

### Staff: Mentor

That does not fully answer my question. That is the frequency that is heard how? When the car is approaching, or when it is stopped and you are stopped. Please post the full text of the question.

7. Mar 20, 2016