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Gravity Unit F, Chapter 1, Section 1 pF6-11. Forces Make Things Move Force: push or pull – Act of objects – Often affect motion of objects Cause objects.

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Presentation on theme: "Gravity Unit F, Chapter 1, Section 1 pF6-11. Forces Make Things Move Force: push or pull – Act of objects – Often affect motion of objects Cause objects."— Presentation transcript:

1 Gravity Unit F, Chapter 1, Section 1 pF6-11

2 Forces Make Things Move Force: push or pull – Act of objects – Often affect motion of objects Cause objects to: – Speed up – Slow down – Stop – Change direction – Gravity – force always acting on us

3 The Force of Gravity Gravitation: every piece of matter in the universe, no matter how large or small, pulls on every other piece of matter Gravity: force that pulls us and everything around us toward the center of the Earth –Gravitation on Earth

4 The Force of Gravity Why are planets and stars round? – Gravity: force that pulls everything to Earths center Pulls on solids: – Us and all objects around us Pulls on gases – Keeps our atmosphere in place » Moon – weaker gravitational pull » Couldnt hold an atmosphere if it had one Pulls on liquids – Holds oceans tight to Earths surface – Keeps ocean levels fairly level

5 The Force of Gravity What causes the tides on Earth? – Attraction between moon and Earths oceans Oceans bulge toward moon on one side of Earth Oceans bulge away from moon on other side of Earth – Remember: Gravitation: every piece of matter in the universe, no matter how large or small, pulls on every other piece of matter – The moon is a piece of matter in universe – The water on Earth is a piece of matter in the universe

6 Mass & Gravity Mass: amount of matter in an object Objects with large masses affect the motion of other objects – Two objects have same gravitational pull on each other Gravity affects movement of smaller objects more – Relationship: Increase mass= stronger force

7 Mass & Gravity Objects with large masses affect the motion of other objects – Earth-sun system: Gravitational force between Earth and sun – Suns force on Earth keeps Earth in orbit – Earths force on sun isnt noticeable – Solar systems with star and very massive planet Gravitational force between massive planet and star – Stars force on planet keeps planet in orbit – Massive planets force on star makes star wobble

8 Mass & Gravity Q: Why dont we see all the objects around us moving toward each other? – Remember: Gravitation: every piece of matter in the universe, no matter how large or small, pulls on every other piece of matter – A: Masses are too small Objects move toward Earth because of large mass

9 Distance & Gravity Gravitational force is affected by: – Mass of objects – Distance between objects More distance between two objects the weaker the gravitational force between them

10 Distance & Gravity Q: Why dont we fly off the Earth toward the sun? (It is 330,000 times as massive as the Earth) A: We are much closer to the center of the Earth – We are much farther from the center of the sun – We feel Earths gravitational force pulling on us more than the suns gravitational force

11 Distance & Gravity Distance between objects affect gravitational force – Compare force of gravity on two people: Person standing at sea-level – Force of gravity is slightly more » Closer to Earths center Person standing on tall mountain – Force of gravity is slightly less » Farther from Earths center – Relationship: Increase distance = weaker force

12 Distance & Gravity Gravitational pull is affected by: – Distance between objects Spacecraft problem – Strong gravitational force when rocket is close to Earth – Need incredible force to escape gravitational pull – Gravitational pull weakens as spacecraft moves farther

13 How Gravity is Measured Scale: instrument used to measure force of gravity – Weight measure of the force of gravity on an object – Newton: SI (metric) unit for weight All forces can be measured in Newtons – Weight is just one type of force – Mass: amount of matter in an object Stays the same no matter where you go in universe Weight depends on gravitational force where object is found

14 Summary Forces act on objects and often change motion Gravitational attraction pulls all objects toward each other Gravitation strength depends on: – Masses of objects As masses increase, gravitational attraction increases – Distance between objects As distance increases, gravitational attraction decreases Forces are measured in Newtons – Including force of gravity

15 Homework Read pF6-11 Answer ?s 1-10 on Goggle Form (or get a printed copy of the questions)


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