Physics wave help

[pizza1994]

If deep-water ocean waves elevate a stationary boat every 4 seconds and the distance between every third crest is 150 m, what is the average speed of the waves?

a) 0.08 m/s

b) 12.5 m/s

c) 37.5 m/s

d) 113 m/s

Answer= B
Source= TBR

dont get how to calulcate frequency. I thought frequency is number of cycles/length of time and so I would think its 3/4........but apparently its 1/4 -_-

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[NextStepTutor_2]

In this question, they give you the time it takes to complete one cycle or, in other words, the period (every 4 seconds). Frequency is defined as cycles per second or the reciprocal of the period (1/4 Hz)

 

[el_duderino]

Every third crest is 150m, so 50m between each crest. 4 seconds between each crest.

50m / 4s = 12.5 m/s

Question doesn't ask for frequency. It asks how fast the waves are moving.

 

[pizza1994]

Every third crest is 150m, so 50m between each crest. 4 seconds between each crest.

50m / 4s = 12.5 m/s

Question doesn't ask for frequency. It asks how fast the waves are moving.

sweet thanks!!! perfect example of unit analysis.