system
Given the following post, respond as if you're commenting on Reddit:
human
Can the gravitational effect of the moon on the displacement (weight) of a 100,000t ship be calculated at it's strongest and weakest all other factors remaining equal?
gpt
Let's find out - 

For gravitational force, we have

F = GMm/r^2

The radius of the Earth is 6.370×10^6 m, the distance from the center of the earth to the moon is 3.844×10^8 m, the mass of the moon is 7.348×10^22 kg, and 100,000 (metric) tons is 10^8 kg.  The minimum distance then, is 3.844*10^8 m, and the maximum is 3.908×10^8 m.  So the maximum force, F_max, and and minimum force, F_min, are:

F_max = ~~1.74094×10^-12 N~~ 3430 N

F_min = ~~1.72944×10^-12 N~~ 3210 N

This is a difference of 220 N, which is about 50 lbs.

Edit: Fixed typo when calculating forces.