1. Gravity and Acceleration

2. And You

3. Gravity  What is Gravity? –1. Gravity = force of attraction between 2 objects as a result of their masses.  On Earth the force between an object on Earth, and the Earth results in what we consider a constant acceleration…  This is because the Earth is so massive in comparison to objects on earth.

4. Aristotle and the bunch  For many years most people believed Aristotle’s belief that heavier objects fall at a faster rate than lighter objects.  Makes sense, right?

5. Groovy Galileo Galileo disputed Aristotle and suggesting that objects on Earth fall at the same rate. No matter their weight.  Through scientific tests he was able to show his theory was Supported by his results!!!  HEAVIER objects DO NOT fall faster than a LIGHTER objects.

6. Acceleration due to Gravity  When air resistance doesn’t influence objects on Earth, they accelerate at 9.8 m/s/s or 9.8 m/s 2.  Acceleration from Gravity = g (always lower case)  Note: g is NOT gravity, just the acceleration due to gravity on earth.

7. ?? 9.8 m/s/s ??  If an object is dropped with no initial velocity then after 1 second it is traveling at a rate of 9.8 m/s (*note it did not travel 9.8 m!!!)  After 2 seconds it is traveling at a rate of 9.8 + 9.8 = 19.6 m/s  After 3 seconds?  9.8 + 9.8 + 9.8 = 29.4 m/s  It did not travel 29.4 m, it has a speed of 29.4 m/s!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

8. What can I do with this? v i = initial velocityv f = final velocity a = acceleration g = acceleration due to gravity t = timed = distance  Calculate final velocity of a falling object. V f = at + v i or v f = gt + v i  Calculate the distance traveled by a falling object. d = 1/2at 2 or d = 1/2gt 2

9. How fast is it falling

10. How far has it fallen?

11. Practice Problems  How far does a ball fall after 2.7 seconds? Position (y) = ½ * g * t 2 (y) = ½ * 9.8(m/s 2 ) * 2.7 2 = 4.9m/s 2 * 7.29s 2 = 35.721 m = 36 m

12. How about some more sweet equations If I throw an object up, how high will it go? y top = v i 2 / 2g How long with the ball stay in the air? t = 2y top / g Where does that come from?

13. A stone is thrown into the air with an initial velocity of 9.8 m/s. How high will it go? Y top = V i 2 / 2g

14. How long with the ball stay in the air from the Y (top) down? (4.9m high) t = 2y top / g

15. Therefore: The total time this object stays in the air from the time of release to the time it returns to the point of release is: 2s Time up = time down