Question

why is the Moon's force of gravity less than that the earth

Answer 1

Earth's gravitational field is created by the mass deep inside the crusr of the earth.but moon doesn't have this much mass so gravitational force will be usually less.
as u know gravitational force depends on the mass according to the equation
F=GMm/R^2

Answer 2

Not only is the Moon smaller than the Earth, but it is only about 60 percent as dense as Earth. Thus, the gravitational attraction on the Moon is much less than it is here on Earth.