[填空题]
A sailor strikes the side of his ship just below thek)3t0y1slrur29 *r rbv zcg7 q waterline. He hex p,gb4e i 3-,ffcjm/sampn8/ars the echo of the sound reflected from the ocean floor directly below 2.5 s later. How deep is the ocean at this point? Assume the speed of sound in seawater is 1560 m/s (Table 12–1) and does not vary seci3fjn-f8,m//pa x,s mb4gpignificantly with depth. $ \times10^{ 3}$m
