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The Force of Gravity
Newton and Gravity
One of the best known stories in science tells of Isaac Newton`s discovery of the law of gravity. In the middle of the 17th century (1666) Newton was a "natural scientist" at Cambridge University in England. During this time he returned to his home to escape the Great Plague. One day he was watching apples dropping from a tree (so the story goes) and it struck him that the same force that attracted apples to the ground also kept the moon in orbit around the earth. Every object possessed a similar kind of attractive force, the force of gravity.
Pull of Gravity
Gravity is a natural attracting or pulling force which exists between any two objects in the universe. The greater the mass of the objects, the greater the force of attraction. The greater the distance between the objects, the weaker the force. The gravitational force between the moon and the earth is about 15 million trillion pounds. This large value is due to the large masses of both objects. The force between everyday object is very weak. Yet the gravitational force between normal everyday objects (insignificant mass) and the earth (very massive) accounts for each object`s weight. The force of gravity on a object is that object`s weight. All matter is pulled downward by gravity towards the earth. No matter how high you jump, you will eventually fall back to earth due to gravity. Gravity affects everyone and everything on earth. If you let go of an object it will be pulled back to earth. This pulling results in motion. Gravity is a force that naturally causes motion.
Falling Objects
Galileo showed in the 16th century that objects fall with a constant acceleration. He believed that the rate of acceleration is the same for all objects no matter of size or composition. This means that large iron balls will fall at the same rate of acceleration as a marble. Although these two objects vary considerably in weight, the heavier item will not fall any faster than the lighter item.