A boat sitting in the trough of a wave takes 3 seconds to reach the highest point of the wave, and the wave's velocity is 5 m/s. What is the wavelength of the wave?

1. Going from the trough to the crest covers only half of one full wave cycle. 2. So the 3 s given is half of the period, meaning T = 2 times 3 s = 6 s. 3. Wave velocity relates wavelength and period by v_w = lambda / T. 4. Rearranging: lambda = v_w times T. 5. Substituting: lambda = 5 m/s times 6 s = 30 m. 6. Option A, 15 m, comes from the trap of treating 3 s as the full period instead of half of it. 7. Option C and D come from dividing instead of multiplying speed and time. _Source: OpenStax Physics (CC BY 4.0), Ch 13 "Waves and Their Properties", section 13.2 Wave Properties: Speed, Amplitude, Frequency, and Period_