1. Gravity and Motion

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

3. Gravity Gravity is 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 gravity on an object The greater the mass the 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. masses of the objects 2. distance between the objects

9. Gravity gravity between the objects. The greater the masses, the greater the gravity between the objects. distanceless The greater the distance, the less the 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 1 m 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 inertia keeps the moon in orbit around the Earth. If there were no gravity, inertia would cause the moon to travel in a straight line. If only gravity existed, the earth would be pulled into the sun.

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