1. Gravity Chapter 11.2

2. Gravity Law of Universal Gravitation- all objects in the universe attract each other through gravitational force Law of Universal Gravitation- all objects in the universe attract each other through gravitational force –Equation: G = gravitation constant; m = mass; d = distance

3. What does that equation tell us? Force between two objects… Force between two objects… Force is directly related to mass (the greater the masses of the objects, the greater the force) Force is directly related to mass (the greater the masses of the objects, the greater the force)

4. Which two objects have a greater force between them? Or

5. What does that equation tell us? Force between two objects… Force between two objects… Force is indirectly related to distance (the greater the distance between two objects, the smaller the force) Force is indirectly related to distance (the greater the distance between two objects, the smaller the force)

6. Which two objects have a greater force between them? Or

7. Gravity on the Earth Since the Earth is so large (large mass!), it exerts a large gravitational force on all objects on the earth Since the Earth is so large (large mass!), it exerts a large gravitational force on all objects on the earth This is why objects are attracted towards the center of earth (why things fall!) This is why objects are attracted towards the center of earth (why things fall!)

8. Speaking of falling… Free fall—the motion of a body when only the force of gravity is acting on the body Free fall—the motion of a body when only the force of gravity is acting on the body Movement is directed towards the center of the earth Movement is directed towards the center of the earth Free fall acceleration (g) on Earth = 9.8 m/s^2 Free fall acceleration (g) on Earth = 9.8 m/s^2

9. Determining Weight… Weight- gravitational force exerted on an object Weight- gravitational force exerted on an object Weight decreases as an object moves away from Earth because gravity decreases Weight decreases as an object moves away from Earth because gravity decreases Weight = mass x free-fall acceleration w = mg Weight = mass x free-fall acceleration w = mg Units for weight = Newton (N) Units for weight = Newton (N)

10. Calculating Weight… On Earth, how much does a 66 kg astronaut weight? On Earth, how much does a 66 kg astronaut weight? Remember, w = mg Remember, w = mg w = (66 kg) (9.8 m/s^2) w = (66 kg) (9.8 m/s^2) w = 650 N (about 150 pounds) w = 650 N (about 150 pounds)

11. Terminal Velocity Terminal velocity—the constant velocity of a falling object when the force of air resistance is equal in magnitude and opposite in direction to the force of gravity Terminal velocity—the constant velocity of a falling object when the force of air resistance is equal in magnitude and opposite in direction to the force of gravity

12. Cat Reaching Terminal Velocity

13. Projectile Motion The curved path that an object follows when thrown, launched, or projected near the surface of Earth 2D motion of objects under the influence of 2D gravity

14. Projectile Motion There are horizontal and vertical components to projectile motion

15. Last video of the chapter… http://www.gpb.org/chemistry- physics/physics/505