Question

A fisherman notices that his boat is moving up and down periodically without any horizontal motion, owing to waves on the surface of the water. It takes a time of 3.00 ss for the boat to travel from its highest point to its lowest, a total distance of 0.680 mm . The fisherman sees that the wave crests are spaced a horizontal distance of 6.10 mm apart.
Required:
a. How fast are the waves traveling?
b. What is the amplitude of each wave?
c. If the total vertical distance traveled by the boat were 0.30 m but the other data remained the same, how would the answers to parts (a) and (b) be affected?

Answer 1

Answer:  

a. Speed = 1.6 m/s  

b. Amplitude = 0.3 m  

c. Speed = 1.6 m/s  

Amplitude = 0.15 m  

Explanation:  

a.  

The frequency of the wave must be equal to the reciprocal of the time taken by the boat to move from the highest point to the highest point again. This time will be twice the value of the time taken to travel from the highest point to the lowest point:

frequency = $\frac{1}{2(2\ s)}$ = 0.25 Hz  

The wavelength of the wave is the distance between consecutive crests of the wave. Therefore,  

Wavelength = 6.4 m  

Now, the speed of the wave is given as:  

Speed = (Frequency)(Wavelength)  

Speed = (0.25 Hz)(6.4 m)  

Speed = 1.6 m/s

b.  

Amplitude is the distance between the mean position of the wave and the extreme position. Hence, it will be half the distance between the highest and lowest point:  

Amplitude = (0.5)(0.6 m)  

Amplitude = 0.3 m  

c.  

frequency = $\frac{1}{2(2\ s)}$ = 0.25 Hz  

Speed = (Frequency)(Wavelength)  

Speed = (0.25 Hz)(6.4 m)  

Speed = 1.6 m/s  

Amplitude = (0.5)(0.3 m)

Amplitude = 0.15 m