Motionchapter2notes5

2-4 Gravity

Objectives:

- Relate gravity and the motion of falling objects
- Explain the effects of air resistance on a falling object.
- State Newton's Law of Universal Gravitation

Vocabulary:

Gravity- Force of attraction that depends on the mass of two objects and the distance between them; responsible for accelerating an object toward Earth,

Law of Universal Gravitation- Law that staes that energy is neither created nor destroyed by ordinary means.

- Late 1550's Galileo dropped two cannonballs at exactly the same time from the top of the Leaning Tower of Pisa in Italy.
- One cannonball had ten times the mass of the other cannonball.
- Scientific Theory at that time believed that the more massive cannonball should have landed first.
- However Galileo proved that they landed at the same time.
- Galileo proved that all falling objects accelerate at the same rate.
- The acceleration of a falling object due to the force of gravity between the object and Earth is: 9.8 meters/second/second.
- Any falling object meets air resistance.
- The greater the area of the object, the greater the resistance.
- As objects fall, the air resistance gradually becomes equal to the pull of gravity, which makes the forces balanced.
- When the forces are balanced, there is no acceleration.
- The object will continue to fall but at a constant velocity.
- The force of gravity increases as the masses of the objects increase.
- Gravitational Force decreases rapidly as the distance between objects increase.
- Weight is a measure of the force of gravity on an object.
- Your weight varies according to the force of gravity pulling on you.