1. Get out paper and something to write with!

2. On a sheet of paper answer the following questions…you may ask a neighbor. 1. What is gravity? 2. What is the value of acceleration due to gravity? (**Hint: You’ve seen this number in science class before!) 3. What happens to the speed of an object as it moves upwards? Downwards? 4. What is the difference between speed and velocity?

4. What would happen if you dropped a baseball out a second-floor window?

5. Describe the speed of the baseball, at the beginning when you let it go, and at the end when it hits the ground

6. Is the speed of the baseball constant or does it accelerate? If it accelerates, at what rate? Do ALL objects fall at the same rate?

7. Free fall – an object is in free fall if it is accelerating due to the force of gravity and NO other forces are acting on it * a ball thrown upward is also in free fall after it leaves your hand

8. Gravity http://www.youtube.com/watch?v=PsIBz40PcQ8

9. Acceleration due to gravity – Objects on Earth accelerate downward at 9.8 m/s 2 In physics, this value is represented by the letter g

10. Acceleration due to gravity g = 9.8 m/s 2

11. What does an acceleration of 9.8m/s 2 really mean? What is happening to the speed?

13. Upward Launches When an object is in free fall, it accelerates downward at 9.8 m/s 2. Gravity causes the acceleration by exerting a downward force. So what happens if you throw a ball upward?

14. The ball will slow down as it moves upward, come to a stop for an instant, and then fall back down

15. As it moves upward, the speed decreases by 9.8 m/sec every second until it reaches zero. The ball then reverses direction and starts falling down. As it falls downward, the speed increases by 9.8 m/sec every second.

16. In this picture, the ball’s initial velocity is +19.6 m/sec and its velocity four seconds later is -19.6 m/sec. How come?

18. What is the ball’s speed after 2 seconds, at the top? What is the ball’s acceleration after 2 Seconds at the top?

19. A ball is thrown straight up into the air. As it moves upward, its speed _________ by _____ each second. As it falls back down, its speed ________ by____ each second. decreases 9.8 increases 9.8

20. What is the difference between speed and velocity?

21. Now let’s do some calculations!

22. The rate of acceleration due to gravity, 9.8m/s 2 is the same for all objects, and is always 9.8m/s 2 on the Earth’s surface. So…

23. Using this formula, the height an object falls (displacement), or the time it is in free fall can be calculated if one of those variables is given

25. If you are given the time an object is in free fall, you can calculate how far it fell OR If you are given the height it fell, then you can calculate the time it took to fall

27. Let’s make this formula easier to use if a free falling object starts at rest.

28. You drop a ball from the edge of a cliff. It lands 4 seconds later.What distance does the ball fall during the 4 seconds?

29. A stone tumbles into a mine shaft and strikes bottom after falling for 47.3 seconds. How deep is the mine shaft?

30. The climber dropped her compass at the end of her 240-meter climb. How long did it take to strike bottom?

31. What if you are only given a speed…How do you calculate displacement? What equation have we already used that involves speed/velocity and acceleration?

32. Gravity and Free Fall At a construction site a pipe wrench strikes the ground with a speed of 24 m/s. Calculate the height the pipe wrench was inadvertently dropped.

33. Wrap-Up Review Gravity/Free Fall What is an example? Acceleration due to gravity Upward launch What is an example? Velocity vs. Speed Formula