1. Free Fall Do heavier things fall faster than lighter things?

2. Free Fall: the movement of an object in response to a gravitational attraction Ignoring air resistance, gravity produces an acceleration we often just call “g”, the acceleration due to gravity. On Earth, the size of “g” is 9.8 m/s 2, but since the acceleration is always downward, the value of the acceleration is a = - g = - 9.8 m/s 2 (approximately -10 m/s 2 )

3. What does this mean? Each second of free-fall, the speed of an object increases by about 10 m/s t = 1s Speed = 10 m/s (actually, it’s 9.8 m/s) t = 2s Speed = 20 m/s (actually, it’s 19.6 m/s) t = 3s Speed = 30 m/s Δ Time (s) Speed (m/s) 1~10 2~20 3~30 4~40

4. Positive or Negative? Up= positive Down = Negative If you throw a ball upward, As it moves upward, its velocity is positive. As it falls back down, its velocity is negative. At the highest position, its velocity is ZERO.

5. What’s the speed? 30 m/s 20 m/s 10 m/s 0 m/s 10 m/s 20 m/s 30 m/s

6. If the ball was thrown upward with a velocity of 50 m/s, how long would it take to reach its highest point? What if the original velocity was 70 m/s? 35 m/s? Does the ball travel the same distance during each second?

7. Aristotle Greek philosopher, b. 384 B.C. It’s OBVIOUS that heavy things fall faster than lighter things. Every object has its own “natural” rate of falling INCORRECT

8. Galileo… Galileo found that, ignoring the effect of the air, all freely falling objects had the SAME acceleration, regardless of their mass or the height from which they were dropped. The Law of Falling Bodies Born in Pisa 1564