# Find The Harmonics! HELP!

#### MissB16

Q: A Spaceship lands on a new planet. The crew decides to measure the speed of sound by blowing across one end of a tube. The tube is 50cm long, and the crew finds one resonant frequency at 1620Hz and the next resonant frequency at 1980Hz. What is the speed of sound? What is the number of each of the harmonics they found? What type of tube is the crew using- open/open, or open/closed?

I found the speed to be 360 m/s, but I have no idea how to find the harmonics! I don't know where to start! Help!

#### Doc Al

Mentor
How did you find the speed?

What's the formula for the harmonics for each type of tube?

#### MissB16

I found the speed by the equation v=lambda*f which both frequencies came out to 360

I'm not sure what the formulas are for the tubes...that's my problem. I don't know how to go about finding the harmonics. Hopefully you physics genius's can help me.

#### Doc Al

Mentor
Last edited by a moderator:

#### MissB16

Honestly 360 is what it says on my answer key and I subtracted 1980 from 1620 so I found lambda by V/f=lambda... the answer key says it's the 9th and 11th harmonics with a open/closed tube...I just need an explanation of how they got that answer.

#### Doc Al

Mentor
Honestly 360 is what it says on my answer key
I'm not disputing the answer, only how you arrived at it. The way to get the answer is to use the formulas for the open and open/closed air columns that are in the links I gave you.

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