# What is gravity? Part 1

What is Gravity
Contributed by:Cole S.
Date of publication: September 29, 2011

Gravity is the force that pulls us to the ground when we jump, and keeps the earth in orbit. The equasion to find out how much of a gravitational pull one obect has on another is FG, Gravity is porportional to mM, the mass of the object, devided by the r2, distance between the objects. Isac Newton made the first law of gravity but, Einstine added to it with the theory of relativity.Everything has a gravitational pull toward it, but, the strainghth depends on the mass of the object (even a bouncy ball has a gravitational pull, but it’s pull is extreamly small). Did you know that the gravitational pull from the moon is what causes the tides.

Figure 1: Bigger mass pulling a smaller mass toward it with gravity

Figure 2: gravity pulling an apple onto Isaac Newton’s head.
Air resistance
Air resistance has a big part with gravity too. If an object is falling air resistance may undermine the speed of the object’s falling speed so it is hard to determine how much pull gravity has on the object minus the air resistance.
GLOSSERY
gravitational: the force of attraction between any two masses.
Undermine: to weaken
CITATIONS
Lafferty, Peter. Encyclopedia of Science: Matter and energy. New York: Macmillan Reference USA, print.

Wikipedia. “Gravity.” Wikipedia. The Wikimedia Foundation, September, 17 2011. Web.

Cindy Devine; Sikora, Teresa; Sikora, Ed. “what is the law of gravity.” Ebsco host. Rourke Publishing, LLC Web.

"Gravity." Britannica Elementary Encyclopedia. Encyclopedia Britannica Online School Edition. Encyclopedia Britannica, Inc., 2011. Web. 26 Sept. 2011.