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A boat at anchor is rocked by waves whose crests are 100m apart and whose velocity is 25m/s. How often do the crests reach the boat?

Here,
wavelength= 100m
speed of sound =25 m/s
:. Frequency of wave = 25/100=1/4=0.25 Hz
:. Crests reach boat 0.25 times
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The distance between 2 consecutive crests = 100 m
​This means the wavelength of the wave = 100 m                                                                                                   
Velocity of the wave = 25 m/s 
Velocity = wavelength/timeperiod  
therefore , timeperiod  = wavelength / velocity  
timeperiod = 100/25 sec = 4/1sec = 4 sec
THEREFORE THE  WAVES ATTACK THE BOAT IN THE ANCHOR EVERY SECONDS .
  • 3
The distance between 2 consecutive crests = 100 m
​This means the wavelength of the wave = 100 m                                                                                                   
Velocity of the wave = 25 m/s 
Velocity = wavelength/timeperiod  
therefore , timeperiod  = wavelength / velocity  
timeperiod = 100/25 sec = 4/1sec = 4 sec
THEREFORE THE  WAVES ATTACK THE BOAT IN THE ANCHOR EVERY SECONDS .
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Velocity = Displacement / time

In this case :

Velocity = 25 m/s

Displacement = 100 m

Time = Displacement / Velocity

= 100/25 = 4

= 4 Seconds.

The crests reach the boat after every 4 seconds.

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