A fisherman fishing from a pier observes that the float on his line bobs up and down, taking 2.4 s to move from its highest to its lowest point. He also estimates that the distance between adjacent wave crests is 48 m. What is the speed of the waves going past the pier?

(A) 20 m/s

(B) 1.0 m/s

(C) 10 m/s

(D) 5.0 m/s

(E) 115 m/s

(c) 10m/s

Explanation:

to find the speed of the waves you can use the following formula:

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:

the answer is (c) 10m/s

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