Gravity is the force that attracts matter together (Northwestern). When an object is under the influence of gravity it is referred to as a free fall object. Two things that always remain true about free fall objects on earth are their acceleration is always at 9.8 m/s/s and they never encounter air resistance. It is true that depending where on Earth these objects are falling the acceleration will change, but they all round to 9.8 m/s/s unless of course they are not on Earth. For example acceleration of free fall objects on the moon is 1.6m/s/s, significantly slower than anywhere on Earth (Crowell, 2011). Free fall objects will pick up speed, accelerating downwards (The PC). There are many equations that are related to free fall motion. The most common is to measure the instantaneous velocity of a free fall object over a period of time which is represented by vi=gt. To get the average velocity over average time the equation that would be used is va=gt/2 (Wikipedia, 2013).
Aristotle believed that heavy objects fell faster than lighter ones, and this was believed for thousands of years but Galileo proved otherwise (Crowell, 2011). Today the correlation of the weight of an object and its speed of falling are constant and only change based on aerodynamics; for instance a paper may hit the ground slower than a pencil due to a greater surface area and more resistance to moving through the air particles. If you crumple it up to stop air resistance they will hit the ground at relatively the same time.
References
Benjamin, C. (n.d.). Acceleration and Free Fall. Light and Matter. Retrieved February 19, 2013, from http://www.lightandmatter.com/html_books/lm/ch03/ch03.html
Equations For a Falling Body. (2013, February 7). Wikipedia. Retrieved February 19, 2013, from http://en.wikipedia.org/wiki/Equations_for_a_falling_body
Gravity and Acceleration. (n.d.). The Physics Classroom. Retrieved February 18, 2013, from http://www.physicsclassroom.com/class/1dkin/u1l5a.cfm
What is gravity? (n.d.). Northwestern. Retrieved February 18, 2013, from http://www.qrg.northwestern.edu/projects/vss/docs/space-environment/1-what-is-gravity.html
