1. The Idea of Gravitation
Ideas, Examples and Theories of Gravitation and how to use it

2. Day 45 In APPhysics 1) Video for next class up: You need it.
2) Exam talk
3) New Topic 6: Rotational and Circular Motion
4) Today: Subtopic: Gravitation

3. QUESTIONS TO START OFF 1) What creates gravity?
2) Does it have a speed?
3) Does it have a maximum range to be felt?
4) Can gravity repel objects instead of attracting?

4. In The Beginning Lets talk about astrophysics
A planet and star is formed when gas clouds get pulled together by gravity and become solid (or dense).
Momentum of the clouds did not change, so the formed planet/star keeps rotating

5. In a formation event, will heavier gases be thrown farther than lighter ones?
The inner planets are rocky, with heavy iron cores. The iron was pulled to the middle during formation because of its larger density than the rocky silicate material.

6. There MUST be an idea that governs pulling atoms together, planets together, planets around stars, and keeps them moving in orbits.
GRAVITY. The attractive force between any two objects.
Whatever Joch, I already know about gravity! That was September, before I grew bitter at the world.

7. Gravity is the attraction between all masses.
It is caused by the warping of space-time by mass itself.
Of the 4 basic forces, it is the WEAKEST

8. Idea 1: Gravitational Field
An object with mass creates a FIELD around it.
This FIELD represents where another object in that region can feel a FORCE from that FIELD.

10. When two OBJECTS are near each other, they experience each others FIELDS, and experience an equal FORCE towards each other.
Are the FORCES experienced by each the same?
Yes…Newtons 3rd Law applies

11. The more MASS an object has, the stronger the field
The more MASS an object has, the stronger the field. The more distance between the objects, the weaker the field.
The mass MAKING the field we call the object. The mass that feels the field is called the test.

12. Example: You are on the earth
Example: You are on the earth. You are the test for the Earth’s field at your center of mass
And the Earth is the test for your field at the Earths center of mass
The forces are equal.

13. Are the FIELDS of each object equal?
No! Earth has more mass, so a stronger field. But your small mass barely interacts with it.
The Earth’s huge mass really interacts with your weak field
The forces from each are equal!

14. To calculate the field strength due to gravitation:
g = G(M/d2),
where: g is the field strength/surface
G is the gravitational constant 6.67x10-11
M is the object mass
d is the distance between the center of masses of the two objects

15. Example

16. Example

19. A steel sphere of mass M and radius r is now replaced by a steel sphere that is three times the radius of the original.
Now what is the surface gravitational field?