At the beach, some waves with wavelength of 100 m propagate towards the shore at a speed of 12. 5 m/s.
(a) With what frequency does an anchored boat bob up and down?
(b) Compare this with how often wave crests would hit the front of the boat as it headed out to sea.
(c) Does the engine sound higher- or lower-pitched to someone standing on the shore, compared with the experience of people on the boat?