1. Newton's law of universal gravitation states that every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them
Section 2-28

2. F is the force between the masses, G is the gravitational constant,
where:
F is the force between the masses,
G is the gravitational constant,
m1 is the first mass,
m2 is the second mass, and
r is the distance between the centers of the masses.
F is measured in newtons (N), m1 and m2 in kilograms (kg), r in meters (m), and the constant G is approximately equal to 6.674×10−11 N m2 kg−2

3. at sea level, a distance of 6.38 x 106 m from earth's center.
Sample Problem #1
Determine the force of gravitational attraction between the earth
(m = 5.98 x 1024 kg) and a 70-kg physics student if the student is standing
at sea level, a distance of 6.38 x 106 m from earth's center.

4. Sample Problem #2
Determine the force of gravitational attraction between the earth (m = 5.98 x 1024 kg) and a 70-kg physics student if the student is in an airplane at feet above earth's surface. This would place the student a distance of 6.39 x 106 m from earth's center.