The gravitational attraction between two objects depends upon the mass of the objects and the distance between them. This relationship is often called the "Universal Law of Gravitation" and can be expressed as
F = k G m 1 m 2 / r 2 (1)
F = gravitational force (N)
k G = 6.668 10 -11 (Nm 2 /kg 2 ) = the Universal Gravitation Constant
m = mass of object (kg)
r = distance between objects (m)
Example - The Gravitational Force (Weight) Acting on a Person on Earth's Surface
The gravitational force (or weight ) acting on a person with mass 70 kg on the earth's surface ( 6.37 10 6 m from the earth's center) can be calculated as
F = (6.668 10 -11 Nm 2 /kg 2 ) (5.98 10 24 kg) (70 kg) / (6.37 10 6 m) 2
= 688.1 (N)
- 5.98 10 24 (kg) = mass of earth
Motion - velocity and acceleration, forces and torque.
Forces, acceleration, displacement, vectors, motion, momentum, energy of objects and more.
Acceleration of gravity and Newton's Second Law - SI and Imperial units.
Acceleration of gravity due to latitude and elevation above sea level.
A body and the center of gravity.
Stability - the center of gravity vs. the center of buoyancy.
An introduction to density, specific weight and specific gravity.
Mass vs. weight - the Gravity Force.