The newton's law of universal gravitation used to describe how a particle attracts every other particle in the universe.
The equation is given by,
Where,
F= Gravitational force
masses of the objects
r= is the distance between the center of their masses
G= Gravitational constant
For our problem we have defined that,
(mass of the moon)
(distance Earth-moon)
G= 6.671*10^{-11}Nm^2/kg^2
M=Mass of a person
We have then,
In the other hand we have the force on m-mass due to earth
Ratio is given by
B) Suppose there is a group of young people surfing in the moonlight. They are directly under the moon. At this time the moon exerts its gravitational effect of the earth that causes the tide to rise. Around 6 hours later, when the earth has moved a quarter of the moon, the force on that point decreases, so the tide drops. However, after another 6 hours, people return and experience the same process. In this case the moon is not above them, but on the other side. This is because the moon having an orbit on the earth, generates an external force, similar to the previous one, but the earth reacts in the opposite way. It is like going in a car and turning it, all people will tend to get out of it, because a centrifugal force is experienced.