Ian G.

asked • 12/13/16

Physics Guitar String problem

A guitar string of length 67 cm and mass per unit length 0.9 g m-1 vibrates at an
unknown frequency and is to be tuned to a reference source of 270 Hz, which is
achieved by altering the tension of the string. Initially a beat note of 20 Hz is
heard and as the tension of the string is increased the beat note is observed to
increase. Determine by how much the tension of the string must be changed to
bring the guitar string to the frequency of 270 Hz.

2 Answers By Expert Tutors


Stephen M. answered • 12/13/16

4.9 (632)

Naval Academy Grad for Math and Science Tutoring

Ian G.

not sure I follow this. Its an 8 mark question one of the longer and harder questions. 
I don't get  f = √(F/(m/L)).
where I know v = √(F/u). u = m/L


Stephen M.

Apologize.  f only equals v in a special case, but they are proportional.  That said, if you have length, then f = v/2L (for the fundamental frequency).  So instead of calculating a ratio of tensions, you have the necessary information to compute initial and required tension.


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