1. 4*4 Newton’s Law of Universal Gravitation: The Ups and Downs of a Roller Coaster
WDYS??? (p382)
MOON VS. JUPITER
WDYT???
Gravity (does/does not) have magnitude and direction, therefore it is a (scalar/vector) quantity.
Since Earth is spherical, the direction of gravity __________ will be different in different places, like Australia.

2. 4*4 Mini Lab
Question: In what direction does the force of gravity act? What factors effect the gravitational force?
Drop a small object.
Which way did it drop?
What is the acceleration of the drop (on Earth)?
What is the name of the FORCE that causes the acceleration?
Is the gravity’s strength the same everywhere in the room? (hyp)
Draw a falling map for the room. (8 “gravitational field” lines, equal spacing)
Is the strength of the gravitational fields the same all throughout the room? (measured by distance between the line) (CER)

3. 4*4 Mini Lab
Question: Is the strength of the Earth’s gravitational field the same all around the earth?
Is the strength of Gravity the same all the way around the earth? (hyp)
Draw a “falling map” for Earth.
Is the strength of the gravitational fields the same all around the Earth? (measured by distance between the line) (CER)

4. 4*4 Mini Lab Question: Is gravity a strong or a weak force?
Pull v. Jumping
Can the student “escape” from the surface fo the earth (even for ½ a second)?
Can the student “escape” from the teacher/partner (even for ½ a second)?
This demonstrates the force exerted by the teacher is _______ than gravity.

5. 4*4 Mini-Lab
ANALYSIS:
In what direction does the force of gravity ALWAYS pull? Explain
Is gravity a strong force? Explain your answer.
As the distance from Earth’s surface increases, the gravitational acceleration (force)_____.

6. The change in acceleration is an
4*4 Mini-Lab
How does distance effect gravitational force?
2. What is the acceleration at the following distances?
i) 10,000km =4m/s/s ii) 20,000km = 1m/s/s
iii) 30,000km =0.44m/s/s iv) 40,000km = 0.25m/s/s
2d) What is the ratio of acceleration at the following distances?
i) 20,000km : 10,000km= : 4 = 1/4
ii) 30,000km : 10,000km= 0.44 : 4 = 1/9
iii) 40,000km : 10,000km= 0.25 : 4 = 1/16
The change in acceleration is an
INVERSE-SQUARE RULE

7. 4*4 Notes INVERSE-SQUARE RULE 
When distance is DOUBLED (×2), the acceleration becomes ¼ its original value
When distance is TRIPLED (×3), the acceleration becomes 1/9 its original value
When distance is QUADRUPLED (×4), the acceleration becomes _____
When distance is ×5, the acceleration becomes _____

8. 4*4 Investigate
INVERSE-SQUARE RULE 
FGravity = 1 d2

9. 4-4 Notes Newton’s Law of Universal Gravitation
Earth’s Gravitational Field is EVERYWHERE!!!
1st object (Earth) = source of the field
2nd object (Penny) = the response/test object
Gravitational Lines 
Direction of force on mass toward center of Earth
Acceleration due to gravity is greater closer to Earth, weaker as you move farther away
They are everywhere and beyond!!!

10. 2. The Inverse-Square Relationship
The force of gravity between two objects decreases by the square of the distance between them
EXAMPLE If distance is tripled (×3), then the force is 1/32 or 1/9 the original force
As an object moves AWAY from Earth,
the force of gravity DECREASES drastically!!!

11. ***The force of gravity is quite weak/small***
Universal Gravitation  all objects have MASS and Earth attracts ALL objects
EXAMPLE an apple falls from a tree
the Moon in outer space
Gravity  the force of attraction between two bodies due to their masses
***The force of gravity is quite weak/small***

12. 3. Newton’s Law of Universal Gravitation
ALL bodies with MASS attract all other bodies with MASS
The force of gravity is DIRECTLY proportional to the 2 masses
EXAMPLE larger the mass, stronger the gravity
smaller the mass, weaker the gravity
c) The force of gravity is INVERSELY related to the square of the distance between the 2 masses
EXAMPLE closer the distance, stronger the gravity
greater the distance, weaker the gravity

13. Example:
Imagine two objects have a gravitational force between them of 20 N, and the MASS of the first object is TRIPLED (x3). What is the new gravitational force between them?
Imagine two objects have a gravitational force between them of 20 N, and the DISTANCE between them is cut to a third (x 1/3). What is the new gravitational force between them?

14. Example:
Two objects have a gravitational force between them of 20 N, and the MASS of the first object is TRIPLED (x3), the mass of the second object is doubled, and the distance between them is increased by a factor of 5. What is the new gravitational force between them?
4-4CU/PTG Worksheet

15. 4*4 TOTD
Acceleration due to gravity is greater __________, weaker as you move __________.
The equation for the INVERSE-SQUARE LAW is _____.
If the force between 2 objects is 500N and the distance is ×5, the new force becomes _____.
The 2 factors that effect gravity are _____ and _____.
Draw the Earth’s Gravity Lines 