Courtesy of the Swiss Cetacean Society

Joe Orca lives in the sea, where sound waves travel at roughly 1500 m/s. One day, as he swims North lazily at v = 3 m/s, he sends out a short pulse of sound waves at a frequency f1 = 10,000 Hz. Exactly 5.2 seconds later, he hears an echo ... but the frequency is now f3 = 10,145 Hz.

"Hmmm," thinks Joe, "could this be lunch?"

1. How far is the target from Joe?
2. How fast is the target moving, and in which direction?
3. If both parties continue at their current velocities, how long until they meet?

P.S. Orcas can be just plain nasty.