Answer:
(c) 10m/s
Explanation:
to find the speed of the waves you can use the following formula:
[tex]v=\frac{\lambda}{T}[/tex]
λ: wavelength of the wave
T: period
the wavelength is the distance between crests = 48m
the period is the time of a complete oscillation of the wave. In this case you have that the float takes 2.4 s to go from its highest to the lowest point. The period will be twice that time:
T = 2(2.4s)=4.8s
by replacing you obtain:
[tex]v=\frac{48m}{4.8s}=10\frac{m}{s}[/tex]
the answer is (c) 10m/s