You can excite waves in a string of length 1.142 m fixed at both ends. You started from an arbitrarily low frequency and increased it slowly. You found two successive harmonic standing waves of frequencies: 209.6 Hz and 233.8 Hz. What is the speed of the wave in the medium in m/s.
Note that the speed of standing waves is zero, because it is composed of two waves of velocities v and -v. The question is about the magnitude of v and the answer is not zero!