What factors determine the force of gravity between two bodies?
The force of gravity (F) depends on the masses of the two bodies (m1, m2), and the distance between the bodies’ centers (r). There is a direct proportion between mass and gravitational force: If you double the mass of one body, the gravitational force between them is also doubled. The gravitational force is inversely proportional to the square of the distance: If you double the distance between the two bodies, the force of gravity is reduced to one-fourth its original value. The equation relating these ideas is: F = G(m1m2)/r2 , where G is the universal gravitational constant equal to 6.67 x 10-11 Nm2/kg2 ( or m3/s2kg). 3. What keeps objects in orbit? (What keeps the moon from falling to the earth or the earth from falling into the sun?) Objects remain in orbit around a massive body due to gravity and their sideways motion. Objects in orbit are moving sideways, approximately at right angles (90 degrees) to the force of gravity. An object would travel in a straight line with a constant
