# Doppler formula help please!

doppler formula help please!:)

Hello, i see the doppler formula in 2 different forms one being f1=f2 (Vw/Vw-Vs) and the other f1=f2/(1+Vs/Vw)

f1= Doppler frequency
f2= Source frequency
Vw= Speed of sound
Vs= Speed of source

the problem i am having is understanding how these are equivalent? how fit they get from one to the other? And how would you solve for Vs in the first doppler equation stated? any help would be greatly appreciated :)

## Answers and Replies

tiny-tim
Science Advisor
Homework Helper
hello chiuda! if you replace Vs by -Vs, they're the same! yes i understand that part but lets say the 2nd eqn was already -vs how does one get from the first equation to the second one? it would be very appreciated if all the steps could be shown thank you :)

Try dividing up and bottom by Vw.

then i would have f2*(1-Vs/Vw) which is not the same as f2/ (1-Vs/Vw) :S

tiny-tim
Science Advisor
Homework Helper
Hello, i see the doppler formula in 2 different forms one being f1=f2 (Vw/Vw-Vs) and the other f1=f2/(1+Vs/Vw)
… lets say the 2nd eqn was already -vs how does one get from the first equation to the second one?
then i would have f2*(1-Vs/Vw)

how do you get that? 