Answer:
Backwash effect
Explanation:
Your friend moved along the shore due to ; The swash effect and the Backwash effect
Swash effect is caused by the upsurge of water up along the slopping front of the beach and this same upsurge in water moves back into the beach in what is known as the backwash effect hence the movement of your friend form where they were in the surf zone to another position still within the surface zone is caused by the BACKWASH EFFECT
Answer:
Time taken, 
Explanation:
It is given that, a small metal ball is suspended from the ceiling by a thread of negligible mass. The ball is then set in motion in a horizontal circle so that the thread’s trajectory describes a cone as shown in attached figure.
From the figure,
The sum of forces in y direction is :


Sum of forces in x direction,

.............(1)
Also, 
Equation (1) becomes :

...............(2)
Let t is the time taken for the ball to rotate once around the axis. It is given by :

Put the value of T from equation (2) to the above expression:


On solving above equation :

Hence, this is the required solution.
Answer:By turning the electrical current off
Explanation:Trust me I took the test
Answer:
wavelength = 24 m
Period = 10 s
f = 0.1 Hz
Amplitude = 4 m
Explanation:
Wavelength:
Since the boats are at crest and trough, respectively at the same time. Hence, the horizontal distance between them is the wavelength of the wave:
<u>wavelength = 24 m</u>
Period:
The period is given as:

<u>Period = 10 s</u>
<u></u>
Frequency:
The frequency is given as:

<u>f = 0.1 Hz</u>
<u></u>
Amplitude:
Amplitude will be half the distance between extreme points, that is, crest and trough:
Amplitude = 8 m/2
<u>Amplitude = 4 m</u>