A 4.0-g string is 0.39 m long and is under tension.The string vibrates at 600 Hz in its third harmonic.What is the tension in this string?
A)250 N
B)200 N
C)160 N
D)290 N
E)340 N

Question

Quizplus · Accepted Answer

The third harmonic is 3 times the fundamental frequency, so the wavelength is 1/3 of the string length. The wave speed is given by v = f*lambda, so v = 600 Hz * 0.13 m = 78 m/s. The tension in the string is given by T = m*v^2/lambda, so T = 0.004 kg * (78 m/s)^2 / 0.13 m = 250 N.

A 40-G String Is 0