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Blank Homeworks

NAME: _______________________, Sect. #_______

Physics 109 Homework # 4
due Wednesday, October 10, 2001

formulae:	open pipe:

speed of sound in air: 340 m/s.

1. A 2 meter king piano string has a fundamental frequency of 50 Hz.
    
   1. find the period of the oscillation: T = ________________ sec.
       
   2. what is the round trip travel time of the wave on this string? (this relates to the slinky experiment in the lab):
       
      round trip time = ______________________ sec
       
   3. what is the speed of propagation of the wave on the string? (speed = distance / time!)
       
      speed = ___________________ m / sec.
       
2. The string of a string bass is 1 meter long. When the string is plucked 1/4 meter from the end of the string, what modes will be missing in the resulting oscillation?
    
   missing modes: ________, _________, _________,
    
3. A guitar string is plucked at a point one-third of the string length away from one end.

                         pluck
                         here:
             |_____________|_____________|_____________|
   

   1. what modes will NOT be present in the ensuing oscillation?
       
      NOT present: ______, ________ , ________
       
   2. The string is now touched lightly at the midpoint. What modes will be present afterwards?
       
      modes still present: ________ , _________, _________,
       
4. An open pipe oscillates in the fundamental mode. Make a graph of the pressure at the various places inside the pipe. Since the pressure keeps changing, show the pressure distribution at three instances one-quarter cycle apart.

                                           ________________________________
   
      pipe:                                ________________________________
   
   
   pressure graph:                         ________________________________
   
   
   

5. how long an organ pipe would you need to play a 40 Hz tone?
    
   length = _____________ m