1. Falling Objects

2. How do objects travel as they fall? Prior to mid-1600’s people believed that objects stayed at a constant velocity as they fell and that this velocity depended on the mass Galileo challenged this belief He suggested that all objects (regardless of mass) accelerate at the same constant rate in the absence of air resistance

4. Through experiment, showed that the distance traveled is directly proportional to the square of time In the absence of air all objects have the same acceleration For objects with a small mass and large surface area, air resistance plays a major roll For ordinary objects, air resistance is negligible

6. No air resistanceAir resistance

7. Acceleration of falling objects is due to gravity’s pull on them Greater the gravity, greater the acceleration produced The value of acceleration due to gravity varies slightly with the elevation and latitude but not enough to matter Acceleration due to Gravity

8. Gravity on Earth Average acceleration on earth g = -9.8 m/s 2 Always a negative number because gravity is always pulling down – even if the object is moving up

9. Question Where would a rock accelerate at the greatest rate: the earth or the moon?

10. Graphically

11. Motion Equations with Falling Objects Substitute g for a and y for x Since gravity pulling down, use g = - 9.8 m/s 2

12. Ex. 1 A ball is dropped from a 70.0 m high tower. How far will it have fallen after 3.00s?

13. Ex. 2 A ball is thrown down a 70.0 m tower with an initial velocity of 3.00 m/s. How far will it travel after 2.00 s? What will its speed be?

14. Ex. 3 A ball is thrown up into the air at 15 m/s. How high will it go? How long before it comes back to his hand?

15. Ex. 4 For the ball in the previous problem. A) how long does it take the ball to reach the max height B) what is the velocity when it hits his hand? C) at what time is the ball 8.00 m above his hand?