Stuck for 2hrs on this frequency question

[icecubz]

The two cars have identical horns, each emitting a frequency of fs = 410 Hz. One of the cars is moving with a speed of 8.0 m/s toward a bystander waiting at a corner and the other car is parked. The speed of sound is 343 m/s. What is the beat frequency heard by the bystander? my attempt at the solution:

fo = 410(343)/(343 - 8.0) = 419.791 Hz

fb = f2 - f1
= 419.791 - 410
= 9.791 Hz


i keep getting 9.79 Hz as my answer. i keep getting it wrong (thats what CAPA is telling me). can some one lead me in the right direction or tell me what I'm doing wrong?

Thank you.

 

[SammyS]

The two cars have identical horns, each emitting a frequency of fs = 410 Hz. One of the cars is moving with a speed of 8.0 m/s toward a bystander waiting at a corner and the other car is parked. The speed of sound is 343 m/s. What is the beat frequency heard by the bystander?

my attempt at the solution:

fo = 410(343)/(343 - 8.0) = 419.791 Hz

fb = f2 - f1
= 419.791 - 410
= 9.791 Hz


i keep getting 9.79 Hz as my answer. i keep getting it wrong (that's what CAPA is telling me). can some one lead me in the right direction or tell me what I'm doing wrong?

Thank you.

Hello icecubz. Welcome to PF !

Does "CAPA" care about significant digits?

 

[icecubz]

Hello icecubz. Welcome to PF !

Does "CAPA" care about significant digits?

yes it does, but if i do use the incorrect amount of sig figs, it tells me to use more or less digits. doesn't penalize for incorrect sig figs.

nevertheless, I've tried entering 9.79, 9.791, and 9.80 and its come up as incorrect.

 

[dinospamoni]

Try

f'= ((c+v)/c)*f

this gives a different frequency, and thus a different beat frequency

 

[Nickie]

Hello,

It's great to see that you are working hard on this frequency question. I understand that you have been stuck for 2 hours and are still struggling to find the correct answer. I can provide some guidance to help you find the right solution.

Firstly, let's review the information given in the question. We know that both cars have identical horns with a frequency of 410 Hz. One car is moving towards a bystander at a speed of 8.0 m/s and the other car is parked. We also know that the speed of sound is 343 m/s.

To find the beat frequency heard by the bystander, we need to use the formula for beat frequency: fb = |f2 - f1|. In this case, f2 is the frequency of the approaching car (fo) and f1 is the frequency of the parked car (fs).

So, let's start by finding the frequency of the approaching car (fo). We can use the formula fo = fs (v + vo)/v, where v is the speed of sound and vo is the speed of the approaching car. Plugging in the values, we get:

fo = 410 (343 + 8.0)/343 = 419.791 Hz

Now, we can plug this value into the formula for beat frequency:

fb = 419.791 - 410 = 9.791 Hz

Therefore, the beat frequency heard by the bystander is 9.791 Hz. I noticed that you were getting the same answer, so it's possible that there might be a rounding error. Make sure to use the correct number of significant figures in your calculations.

I hope this helps you find the correct answer. Keep up the good work and don't give up. Science can be challenging, but with persistence and determination, you will find the right solution. Good luck!