posted by johnny .
The Sun and Earth each exert a gravitational force on the Moon. What is the ratio FSun/FEarth of these two forces? (The average Sun-Moon distance is equal to the Sun-Earth distance.)
The ratio of the forces is
Dearth is the average earth-moon distance and Dsun is the average moon-sun (or Earth-sun) distance.
The relative influence upon tides is different from this number. It depends upon the gradient, not the force itself.