1. Universal Gravitation

2. Newton’s Law of Universal Gravitation
Gravitational force is the mutual force of attraction between all masses.
Equal and opposite forces on each object.
Why does the earth not fall into us?
Only HUGE masses create a noticeable gravitational pull.

3. Newton’s Law of Universal Gravitation
G: Universal Gravitational Constant
r: Distance between the centers of each mass

4. Gravitational Fields Visual Demonstration of Gravitational Fields
Two masses create a Gravitational Force.
One mass cannot create a Gravitational Force.
Single masses create Gravitational Fields.
The interaction of two fields causes a force.
Visual Demonstration of Gravitational Fields

5. Orbit
Gravitational Force is the centripetal force that causes the orbit of stars, planets, etc.
Centripetal force pulls toward the center, so why does the moon not fall into the Earth?
Is orbit possible in the earth’s atmosphere?
Smaller objects revolve around larger objects because of the strength of their gravitational fields.

6. Orbit & Centripetal Force
So:

7. Weightlessness Weightlessness on Earth
Gravitational Force reaches an infinite distance.
How does and astronaut experience weightlessness?
All objects around them are ‘falling’ at the same rate.
If there is nothing pushing back (normal force) you do not feel as though you have weight.
Weightlessness on Earth