A bat moving at 6.5 m/s is chasing a flying
insect. The bat emits a 37 kHz chirp and
receives back an echo at 37.65 kHz.
At what speed is the bat gaining on its
prey? Take the speed of sound in air to be
336 m/s. Answer in units of m/s
1 answer
http://www.physics.utoronto.ca/~poptor/solutions05/pss4_optics.pdf