1. Chapter 13 Forces in Motion
Section 1
Gravity: A Force of Attraction

2. Sir Isaac Newton The Law of Universal Gravitation
Newton realized that the same unbalanced force acted on the apple, the moon and every other object that has mass
He called this unbalanced force of attraction - gravity.

3. Gravitational Force Gravitational force increases as mass increases.
Gravitational force decreases as distance increases.

4. Gravity
Gravity is a force of attraction between objects that is due to their masses.
Weight is a measure of the gravitational force exerted on an object.

5. Weight vs. Mass
Your weight is determined by a spring scale. If you weighed 100 lbs. here on earth you would weigh only about 17 lbs. on the moon. Why? Because the moon is one sixth of the Earth’s mass and attracts you with only one sixth of the Earth’s gravitational force.
Your mass is the same on the moon as it is on the Earth.

6. TTFN