1. FREE-FALL

2. POE: With your neighbor
PREDICT
EXPLAIN
OBSERVE

3. POE: Free Fall
Drop a bowling ball and a feather in the worlds largest vacuum chamber
PREDICT: which will hit the ground first, the bowling ball or the feather
OBSERVE:
4min10sec
With your neighbor try to explain what you observed
Share out with the class

4. GRAVITY: AN ATTRACTIVE FORCE

5. NEWTON’S THEORY OF GRAVITY
An Attractive Force
Fg = Gm1m2/r²
G = gravitational constant  6.67 E -11 m³/kg-s²

6. FALLING OBJECTS Free falling bodies undergo constant acceleration.
In the absence of air resistance all objects dropped near the surface of a planet fall with the same constant acceleration.
The free-fall acceleration is denoted with the symbol g or ag.
At the surface of Earth the magnitude of g is approximately -10 m/s² .The negative sign denotes downward direction.

7. AN APPLE AND A FEATHER DROPPED IN A VACUUM CHAMBER

8. FREE-FALL WITHOUT AIR RESISTANCE

9. FREE-FALL WITH AIR RESISTANCE

10. AIR RESISTANCE AND TERMINAL VELOCITY

11. TERMINAL VELOCITY

12. VELOCITY INCREASES AS AN OBJECT FALLS TO EARTH

13. WHAT GOES UP MUST COME DOWN
All objects thrown into the air have a downward acceleration whether they are moving up or down.
At the very top of its path, the object’s velocity is zero, but the ball’s acceleration is –10 m/s² at every point.
Though acceleration is constant the velocity is changing (slows as an object goes up and moves faster as an object falls to Earth).

14. GRAPHING ACCELERATION OF GRAVITY

15. EQUATIONS FOR FREE-FALL
v = velocity t = time
a = acceleration Dy = displacement
v = vo + at  If vo=0 then
Dy = vot + ½ at2  If vo=0 then
v = at
Dy = ½ at2

16. QUESTIONS What is the acceleration of an object in free-fall?
For a falling object, describe how the distance per second change?
How does air resistance affect falling objects?
About 10 m/s2 or 10 m/s/s
Each second of free fall, an object falls a greater distance than it fell in the previous second
Air resistance slows objects with more surface area (flat paper) than more compact objects (crumbled paper).

17. PROBLEMS
How far will a freely falling object fall from rest in five seconds?
Dy = ½ at2
Dy = ½ (-10 m/s2)(5s)2
Dy = -125 m

18. PROBLEMS
A sky diver steps from a high-flying helicopter. If there were no air resistance, how fast would she be falling at the end of a 12 second jump?
v = at
v = (-10 m/s2)(12 s)
v = -120 m/s

19. PROBLEMS Dy = ½ at2 Dy = ½ (-10 m/s2)(1.5 s)2 Dy = -11.25 m
An apple drops from a tree and hits the ground in 1.5 seconds. Calculate how far it falls.
Dy = ½ at2
Dy = ½ (-10 m/s2)(1.5 s)2
Dy = m