posted by Phil .
A standing is generated by two waves which have a velocity of 20 m/s, and go through 10 cycles in 2 seconds. How far is it from the 2nd node to the 7th node of standing wave?
The frequency of each of the two waves is f = 10/2 = 5 Hz and wavelength is V/f = 4 meters. The distance between nodes of a standing wave is half a wavelengh (2 meters). There are five half-waves between the second and seventh node.
Put it all tgether for the answer.