Gravity Introduction

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Gravity is the attractive pull between any two objects. For instance, when an astronaut is on the moon she feels the pull toward the center of the moon – not the center of Earth.




All objects have gravity.


Aristotle incorrectly believed that a heavy object would fall faster than a lighter one. However, Galileo proved that all objects accelerate the same in the absence of air.


an01125_         an01709_



Newton's Law of Gravitation = "Any two bodies in the universe attract each other with a force that is directly proportional to their masses and inversely proportional to the square of their distance apart.”






an01125_               fd00839_

Gravity depends on the mass of objects and the distance between them!




“…directly proportional to their masses”

= Bigger objects exert more gravity than smaller ones.



jupiter          earth



Jupiter exerts more gravity than Earth.


Small asteroids don’t have enough gravity to pull themselves into a round shape!




Larger planets with more gravity have smaller mountains. Planets with more gravity pull their peaks down.




Meanwhile, smaller planets with less gravity have larger mountains.



“…inversely proportional to the square of their distance apart” = closer objects exert more gravity than objects that are far away.





Earth’s gravitational pull has more influence on us because we are close to earth.





You weigh less when you fly at 35,000 feet above the Earth! This is because the force of gravity is less. Your mass remains the same, however.







BD08124_100 Kg

Mass = the amount of material in an object.




BD08124_100 Kg


Weight = mass x gravity

              = 100 Kg x 9.8 m/s/s

              = 980 Newtons


Weight is a force.