FREE-FALL http://liverpoolmilitaryshow.com/page6.htm

POE: With your neighbor PREDICT EXPLAIN OBSERVE

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: https://www.youtube.com/watch?v=E43-CfukEgs 4min10sec With your neighbor try to explain what you observed Share out with the class

GRAVITY: AN ATTRACTIVE FORCE

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

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.

AN APPLE AND A FEATHER DROPPED IN A VACUUM CHAMBER http://apps.cmsfq.edu.ec/holtphysics/Physics/hf2nech02.pdf

FREE-FALL WITHOUT AIR RESISTANCE http://www.physicsclassroom.com/mmedia/newtlaws/efff.cfm

FREE-FALL WITH AIR RESISTANCE http://www.physicsclassroom.com/mmedia/newtlaws/efar.cfm

AIR RESISTANCE AND TERMINAL VELOCITY http://www.physicsclassroom.com/mmedia/newtlaws/efar.cfm

TERMINAL VELOCITY http://hypertextbook.com/facts/JianHuang.shtml

VELOCITY INCREASES AS AN OBJECT FALLS TO EARTH

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).

GRAPHING ACCELERATION OF GRAVITY

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

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).

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

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

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 = -11.25 m