"Gravity is a force of attraction that exists between any two masses, any two bodies, any two particles. Gravity is not just the attraction between objects and the Earth. It is the attraction that exists between all objects". (NASA gravity 2000) Gravity is a very essential part of life on earth. We are in the exact position in the sun's gravitational field to keep us in orbit and keep life ongoing on our planet. Gravity is a downward force on any body of mass, the larger the mass of the body, the stronger the gravitational force. On earth the force is 9.8 N/Kg (Newton's per Kilogram) roughly, depending on where you are on earth.
The original idea of gravity was discovered by Sir Isaac Newton (Jacob 1999). It is said that Newton was sitting under
an apple tree and an apple fell from the tree striking him on the head. (What probably happened was that he watched an apple fall from a tree.) He concluded that there must be a force pulling all objects towards the ground, such as the apple and himself, and because the apple started at rest, there must be acceleration due to that force. Later with his invention of the telescope, he discovered that larger bodies have a stronger gravitational pull. It had been previously proven that the earth and other planets orbited around the sun. Because the sun was the largest body in the solar system, Newton concluded that larger bodies had larger and stronger gravitational fields.
As seen above, gravity is a force affecting 2 bodies. This is not totally exact because it does not factor in air resistance and friction. Even though gravitational acceleration is constant, air resistance affects free fall. For instance, if you took a sky diver and a ball of lead that weighed the same, and dropped them from an airplane at the same time, the sky diver could spread his arms, which would cause resistance and slow his fall. The lead ball would reach the ground first. If the skydiver streamlined himself...
Bibliography: Gravitation, an Encarta Encyclopedia Article Titled Gravitation
(December 18 2000)
Hirsch, A (1986) Physics For a Modern World
Canada, John Wiley & Sons Canada Limited
Gravity and Tides
(December 19 2000)
(Decemer 17 2000)
Jacob, M C. (1999). Newton, Sir Isaac. In World Book multimedia Encyclopedia [CD-ROM]. Sandiago California, United States of America IBM/World Book, Inc
Please join StudyMode to read the full document