Answer:
The velocity ([tex]v[/tex]) of the wave is 3.08 [tex]ms^{-1}[/tex].
Explanation:
According to the figure, the distance ([tex]\large{L}[/tex]) between a trough and its adjacent crest is [tex]\large{L = 3 m}[/tex]. Also the wavelength ([tex]\large{\lambda}[/tex]) of the wave is [tex]\large{\lambda = 2L}[/tex]. Pepe and Alfredo count 11 crests to pass the raft in [tex]\large{t}[/tex] = 21.5 s.
So, the time period ([tex]\large{T}[/tex]) of oscillation of the wave is
[tex]\large{T} = \dfrac{t}{11} = \dfrac{21.5}{11} = 1.95s[/tex]
So, the velocity ([tex]\large{V}[/tex]) of the wave is
[tex]\large{V = \dfrac{\lambda}{T} = \dfrac{2 \times L}{T} = \dfrac{2 \times 3}{1.95}= 3.08 ms^{-1}}[/tex]