1. Free Fall & Projectiles Chapter 3, sections 7-9 & Chapter 8, sections 1-4

2. Free Fall The acceleration of gravity (g) for objects in free fall at the earth's surface is 9.8 m/s 2. Galileo found that all things fall at the same rate.

3. Free Fall The rate of falling increases by 9.8 m/s every second. Height = ½ gt 2 For example: ½ (9.8 )1 2 = 4.9 m ½(9.8)2 2 = 19.6 m ½ (9.8)3 2 = 44.1 m ½ (9.8)4 2 = 78.4 m

4. Free Fall A ball thrown horizontally will fall at the same rate as a ball dropped directly. Horizontal and Vertical Forces are INDEPENDENT of each other

5. Free Fall A ball thrown into the air will slow down, stop, and then begin to fall with the acceleration due to gravity. When it passes the thrower, it will be traveling at the same rate at which it was thrown.

6. Free Fall An object thrown upward at an angle to the ground follows a curved path called a parabola.

7. Projectile Motion Projectile: a body in free fall that is subject only to the forces of gravity and air resistance projectiles. Bodies projected into the air are projectiles. Examples of moving body as projectile: Shot putt High jumper Long jumper Soccer ball Baseball Ski jumper

8. Projectile Motion The ball is in free fall vertically and moves at constant speed horizontally!!!

9. Projectile Motion

10. There is NO acceleration horizontally!!! Gravity results in a horizontal acceleration as the cannonball drops to the ground.

11. Air Resistance In air… –A stone falls faster than a feather Air resistance affects stone less In a vacuum –A stone and a feather will fall at the same speed.

12. Air Resistance Free Fall –A person in free fall reaches a terminal velocity of around 54 m/s –With a parachute, terminal velocity is only 6.3 m/s Allows a safe landing

13. Air Resistance Ideal angle for a projectile –In a vacuum, maximum distance is at an angle of 45 o –With air resistance (real world), angle is less Baseball will go furthest hit at an angle of around 40 o