Gravity and Motionnnnnnnnnnnnnnnnnnn.ppt

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1. Gravity and Motion

2. Isaac Newton
•Isaac Newton was the first person
to hypothesize that the forcethat
pulls an apple to the ground also
pulls the moon toward Earth,
keeping it in orbit.

3. Gravity
•Gravityis a force that attracts all objects
toward each other.
•The force of gravity is measured in units
called Newtons (N).
•http://www.brainpop.com/
(Gravity)

4. Mass vs. Weight
•Mass-is the amount of matter in an
object
•Weight-is the force of gravityon an
object
•The greater the massthe greater the
force(weight)

5. Weight
•With out air resistance everything falls at
the same speed. It’s called Free Fall.
•It just so happens that on earth free fall has
an acceleration of 9.81 m/s
2
•This means we can caclualte weight!

6. Wieght
•Weight is a force so…….
•Weight is equal to mass time acceleartion of
free fall.
•W= mg g = 9.81m/s
2

7. Gravity of two objects
•Any two objects will exert a gravitational
pull on each other.
•So why does the earth not move towards
us??

8. Gravity
•The strength of gravity between two
objects depends on two factors:
•1.massesof the objects
•2.distancebetween the objects

9. Gravity
The greaterthe masses, the greater the
gravity between the objects.
The greater the distance, the lessthe
gravity between the objects.

10. Law of Universal Graviation
•Newton realized that this relationship
between mass, distance and gravity could be
mathematically shown.
•F = G m
1m
2
d

11. Why do Earth and the moon
remain in their orbits?
•Inertia and gravity combine to keep Earth
in orbit around the sun and the moon in
orbit around the Earth.
•A combination of gravity and inertiakeeps
the moon in orbit around the Earth. If
there were no gravity, inertiawould cause
the moon to travel in a straight line. If only
gravityexisted, the earth would be pulled
into the sun.

13. Your weight on other worlds
•http:/www.exploratorium.edu/ronh/weight/