Gravity & MotionStrength of GravityThe law of gravity states that every object in the universe attracts every other object. The strength of gravity increases as mass increases. The strength of gravity decreases as distance increases. Both the Earth and Moon exert gravitational pulls on each other. Earth & Moon have InertiaInertia is the tendency of an object to resist change once it is in motion. An object will stay in motion at a constant speed and direction, unless it is acted on by another force. The Moon and the Earth are in constant motion as they rotate on their axes, and therefore they have inertia.Gravity of the Earth & MoonThe Earth has a greater gravitational pull on objects because it has a larger mass than the Moon. Earth’s gravitational pull is about six times greater than the Moon’s gravitational pull. On the Moon, you would weigh about one-sixth of your weight on Earth.Gravity, Inertia and OrbitThe combination of gravity and inertia keeps the Moon moving in orbit around the Earth. If there were no gravitational pull on the Moon, it would move in a straight line away from the Earth into space. If the Moon did not have inertia, then it would be pulled by Earth’s gravity and crash into Earth. The same forces keep the Earth in orbit around the Sun.Moon’s orbitMoon’s orbitloss of inertiaPhotos courtesy of NASA.© Copyright NewPath Learning. All Rights Reserved. 94-4590Visit www.newpathlearning.com for Online Learning Resources.EarthEarthMoonMoonThe law of gravity states that every object in the universe attracts every other object. The strength of gravity increases as mass increases. The strength of gravity decreases as distance increases. Both the Earth and Moon exert gravitational pulls on each other. Inertia is the tendency of an objeeeeeecccccccccccccccttttttttttt tttttttttttooooooooooooo resist change once it is in motionn. AAAAAAAAAAAAAAAAAAnnnnnnnnnnn object will stay in motion at a constanntttttttttt speed and direction, unless it is acted on by another force. The Moon annnnnnnddddddddddddd tttttttttthhhhhhhhhheeeeeeeeeee Earth are in constant motttttttttttttiiiiiiiiiiioooooooooooonnnnnnnnnnnnn aaaaaaaaaaaassssssss ttttttttthhhhhhhhhhhheyyyyyyyyyyy rotate on their axes, andddddddd ttttttttttttthhhhhhhhhhhhhhhheeeereffffffffffffoooooooooooooorrrreeeeeeeeeeeee tttttttttthhhhhhhhhhhhhhey have inertia.TTTTTTTTTTTTTTTTThhhhhhhhhhhhhhhheeeeeeeeee Earth has a ggggggggggggggrrrrrrrrrrrrreeeeeeaaaaaaaaaaaaaaaaaattttttteeeeeeeeeeeerrrrrrrrrrrrrr gggravitational pullooooooooooonnnn ooooooooooobjeccccccctttttttttssssssssssss bbbbbbbbbbbbbbbbbbbbeeeeeeeeeeecccccccccccccaaaaaaaaaaauuuuuuuuuuuuussssssssssseeeeeeeeeeeee iiiiiiiiiiiiitttttttttt hhhhhhhhhhhhhas a larger mass thhhhhhhhhhhhan thhhhhhhhhhhhhhheeeeeeeeeeeeeee MMMMMMMMMMMMMMMMMMMoooooooooooooooooooooooooooonn. Earth’s gravitational pull is abbbbbbbbbbbbbbooooooooooooooouuuuuuuuuuuuuuuuutttttttttttt ssssssiiiiiiiiiiiixxxxxxxxxxxxxxxx tttttttttttiiiiiiiiiimmes greater than theMooooooooooonnnnnnnnnnnnnn’’’’’’’sssssssssssss ggggggggggggraviiiiiiiiitttttttttttaaaaaaaaaaaaatttttttttttttiiiiiiiiiiiooooooooooonal pull. On the Moon, yyooooooooooooooooouuuuuuuuuuuuuuu wwwwwwwwwwwwwwwwooooooooooooouuuuuuuullllllllldweeeeeeeeeiiiiiiiiiigggggh about one-sixth of your wwwwwwwwwwwwwwwwwweeeeeeeeeeeeeeeeiiiiiiiiiiiiiiiigghhhhhhhhhhtttttttttttt ooooooooooooooonnnnnnnnnnnnn EEEEEEEEEEEEEaaaaaaaaaaaaaaaarrrrrrrrrrrrttttttttth.The combinaaaaaaaaaaaaattttttttttttttiiiiiionnnnnnnnnnnnnn ooooooooooofffffffffff ggggggggggggggggraaaaaaaaaaaavvvvvvvvvvvvviiiiiiiiiittttttyyyyyy aaaaaaaaaaaannnnnnnnnnnnnndddddddddddd inerrrrrrttttttttttttiiiiiiiiiiiiiaaaaaaaaaaaa kkkeeeeeeeeepppppppppppppppppsssssssssssss the Moon mmmmmmmmmmmmmmmmoving in orbit around the Earth. If there were no gravitational pull on theeeeeeeeeee MMMMMMMMMMMMooooooooooooooooooooooooooooonnnnnnnnnnnn,,,,,,,,, iiiiiiiiiiiittttttt wwwwwwwwwwwwwwoulllllllllldddddddddddddd mmmmmmmmmmmmovvvvvvvvvvvvveeeeeeeeeeeeeee iiiiiiiiinnnnnn a sttttttttttrrrrrrrrrrraaaaaaaaaaaaaaiiiiiiiiiiiigggggggggggggghtt lllllllllllliiiiiiiiiiiiiiiiinnnnnnnnnnnnnnnnneeeeeee away from the Earth into space. If the Moon did not have inertia, then it wwoooooooooooooouuuuuuuuldddddddddddddddd bbbbbbbbbbbbbbbbbbeeeeeeeeeeee pppppppppppppuuuuuuuuuuuuuuulllllllllllllllllleeddddddddddddd by Earrrrrrrttttttttttthhhhhhhhhhhhhhhhhh’ssssssss ggggggrrrrrrrrrrrraaaaaaaaaaaaavvvvvvvvvvvviity annnnnnnnnnnnnnnnddddddddddddddddd cccccccrassssssssshhhhhhhhhhhhhhhhhh into Earth. The same forces keep the Earth in orbit around the Sun.MoonM’s orrrrrrrrrrrbbbbbbbbbbbbbbbiiiiiiiiiiiittttttttttttbbbMoonM’s orbitloss of inertiar if nEarthEarthMMMMMMMMMMMMMooooooooooooooooooooooooooooonnnnnnnnnnnnnnnMoon
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