Tuesday, March 7, 2017

Test Practice with answers!

1.  How long should an tube (open at both ends) be in order to have a resonant frequency (n=1) of 262 Hz?  (This is C below concert A.)  Assume that the speed of sound is 340 m/s.

2.  How long should a pendulum be so that it swings 3 times per second?

3.  A string is 0.40-m long and has a wave speed of 60 m/s.  Find the wavelengths and frequencies of the first 3 harmonics.

4.  A tube open on both ends is 1.0-m long.  What is the resonant frequency (n=1) of this tube?  Assume that the speed of sound is 340 m/s.  What are the frequencies of the next 2 harmonics?


Answers

1.  0.65 m

2.  f = 3 Hz.  T = 1/3 sec.  L = 0.027 m

3.  0.8 m, 0.4 m, 0.266 m.
     75 Hz, 150 Hz, 225 Hz

4.  170 Hz, 340 Hz, 510 Hz



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