1. Free Fall and Acceleration of Gravity Rene Smith

2. Introduction to Free Fall What causes an object to free fall? “Free-falling objects do not encounter air resistance” “Skydiving is not free falling because a human experiences air resistance as they jump out of a plane” The longer an object free falls, the faster it will fall GRAVITY

3. But wouldn’t anything that is dropped experience air resistance? No. To free fall an object must: -be heavy in weight -fall for a moderately short amount of time - move fairly slow

4. However, to be in free fall does not necessarily mean that an object must be traveling in a downward direction. “All free-falling objects (on Earth) accelerate downwards at a rate of 9.8 m/s^2”

5. Free Fall In Action If you were to drop a softball and a piece of paper from the same height, at the same time, which object would experience free fall? The softball. The piece of paper experiences air resistance.

6. The Acceleration of Gravity Merriam-Webster Dictionary defines the acceleration of gravity as “the acceleration of a body in free fall under the influence of earth's gravity expressed as the rate of increase of velocity per unit of time” This standard numerical value is so important to scientists that it was given its own special name— the symbol g.

7. How is it calculated? The standard value of g is 9.8 m/s/s, which is often rounded up to 10 m/s/s for rough calculations. Air resistance: the force of air molecules striking a moving object In the absence of air resistance, all objects will accelerate at the same rate ▫This constant velocity is called terminal velocity ▫At this point, the object is said to be in “free fall”

8. More with Calculations A= ∆v = -9.8m/s t 1 s Positive (+) shows the UP direction Negative (-) shows the DOWN direction ▫When calculating for free fall, always use the negative direction. When solving problems in free fall, use any of the following formulas. -v f = v i + at -d = ½ (v f + v i )t -d = v i t = ½ at 2 -v f 2 = v i 2 + 2ad Write the givens, figure out which variable you want to solve for, and determine which formula to use to find that answer.

9. Just for Fun! Due to variations in latitude, longitude, and geological structure of various regions of the world, there are some slight differences in the value of the acceleration of gravity here on Earth. These are based off gravitational fields. LocationTotal Gravitational Acceleration Buchanan, Virginia9.79934 m/s 2 Paris, France9.81289 m/s 2 San Francisco, California9.80035 m/s 2 Tokyo, Japan9.79805 m/s 2

10. “Free Fallin” Graphs

12. This graph is representing the velocity. On this Velocity vs. time graph the line is straight. Since a free-falling object is undergoing an acceleration (g = 9.8 m/s/s, downward), it would be expected that its velocity- time graph would be diagonal. A further look at the velocity-graph reveals that the object starts with zero velocity and finishes with a large, negative velocity.

13. Terminal Velocity Terminal Velocity is the term that many scientists use to show that an object has reached when the force of drag acting on it is equal to the force of gravity acting on the object in free fall.

14. Sources http://www.skydive-dc.com/ http://www.physicsclassroom.com/class/1dkin/u1l5e.cf mhttp://www.physicsclassroom.com/class/1dkin/u1l5e.cf m http://www.physicsclassroom.com/class/1dkin/U1L5a.c fmhttp://www.physicsclassroom.com/class/1dkin/U1L5a.c fm http://www.batesville.k12.in.us/physics/phynet/mecha nics/kinematics/FreeFallIntro.htmlhttp://www.batesville.k12.in.us/physics/phynet/mecha nics/kinematics/FreeFallIntro.html http://www.angelfire.com/psy/freefall/freefall.htm http://www.hometeamsonline.com/teams/default.asp?u =WVHSSOFTBALL&sport=softball&t=c&p=home&s=so ftballhttp://www.hometeamsonline.com/teams/default.asp?u =WVHSSOFTBALL&sport=softball&t=c&p=home&s=so ftball http://foundinapieceofpaper.blogspot.com/2010/10/tod ay-my-mom-scolded-me-for-wanting-to.htmlhttp://foundinapieceofpaper.blogspot.com/2010/10/tod ay-my-mom-scolded-me-for-wanting-to.html

15. Sources http://www.merriam- webster.com/dictionary/acceleration%20of%20grav ityhttp://www.merriam- webster.com/dictionary/acceleration%20of%20grav ity http://www.physicsclassroom.com/class/1dkin/u1l5 b.cfmhttp://www.physicsclassroom.com/class/1dkin/u1l5 b.cfm http://www.wolframalpha.com/widget/widgetPopu p.jsp?p=v&id=d34e8683df527e3555153d979bcda9c f&title=Gravitational%20Fields&theme=red&i0=Bu chanan%2C%20VA&podSelect=&includepodid=Inp ut&includepodid=GravitationalFieldStrengthhttp://www.wolframalpha.com/widget/widgetPopu p.jsp?p=v&id=d34e8683df527e3555153d979bcda9c f&title=Gravitational%20Fields&theme=red&i0=Bu chanan%2C%20VA&podSelect=&includepodid=Inp ut&includepodid=GravitationalFieldStrength Our textbook notes

16. Sources http://www.physicsclassroom.com/class/1dkin/ U1L5c.cfmhttp://www.physicsclassroom.com/class/1dkin/ U1L5c.cfm http://hypertextbook.com/facts/JianHuang.sht mlhttp://hypertextbook.com/facts/JianHuang.sht ml http://www.wisegeek.com/what-is-terminal- velocity.htmhttp://www.wisegeek.com/what-is-terminal- velocity.htm http://tap.iop.org/mechanics/drag/209/page_4 6353.htmlhttp://tap.iop.org/mechanics/drag/209/page_4 6353.html