1. Gravity The force of attraction between objects that is due to their masses

2. All matter has mass, so all matter experiences gravity. All matter has mass, so all matter experiences gravity.

3. The Law of Universal Gravitation Stated by Sir Isaac Newton (1642-1727) Stated by Sir Isaac Newton (1642-1727) “All objects in the universe attract each other through gravitational force. The size of the force depends on the masses of the objects and the distance between them.” “All objects in the universe attract each other through gravitational force. The size of the force depends on the masses of the objects and the distance between them.”

4. Mass vs. Weight Mass is the amount of matter in an object. Mass is the amount of matter in an object. (Measured in grams or kilograms) Weight is the measure of the gravitational force exerted on an object. Weight is the measure of the gravitational force exerted on an object. (Measured in Newtons) (Measured in Newtons) Why do we weight less on the moon? Why do we weight less on the moon? -Because the moon has less mass than the earth. earth.

5. How many Newtons do you weigh? 1. Convert lbs. to kg 1. Convert lbs. to kg (Weight in pounds X 0.4536) (Weight in pounds X 0.4536) 2. Convert kg to Newtons 2. Convert kg to Newtons (Weight in kg X 9.8) (Weight in kg X 9.8) Ex. 190 lbs X 0.4536 = 86.18 kg 86.18 kg X 9.8 = 844.60 N 86.18 kg X 9.8 = 844.60 N

6. Acceleration due to gravity 9.8 m/s/s – the rate at which all objects fall towards earth (ignoring air resistance.) 9.8 m/s/s – the rate at which all objects fall towards earth (ignoring air resistance.)

7. Terminal Velocity Is the point at which a falling object stops accelerating and begins to fall at a constant speed. Is the point at which a falling object stops accelerating and begins to fall at a constant speed. If there were no atmosphere there would be no air resistance. (That’s why a feather and a rock would land at the same time if dropped on the moon.) If there were no atmosphere there would be no air resistance. (That’s why a feather and a rock would land at the same time if dropped on the moon.)