1. Universal Law of Gravity, Orbits, and Weightlessness
Chapter 9 – pages ONLY
Also part of chapter 10, pages

2. Student Learning Outcomes
Understand the conditions that lead to weightlessness
Give examples of weightlessness other than objects in space
Understand universal law of gravity and inverse square laws
Calculate changes in gravitational forces as parameters change

3. Weightlessness When have YOU felt weightless? [ignore being in water]
Weightless when you _________________ __________________________________
Weightless scenes in Apollo 13 were filmed this way!
Read about this on pages
When you read:
Keep “_________ weight” in mind
“___________ weight” is ______________.
__________________________________.

4. Falling Around Newton’s cannon drawing.
Put your drawing here:
Newton’s cannon drawing.
Gravity’s __________ _____________________ ___________
See pages in chapter 10 for more info.
These cannonballs ____________ ____________________________ _________________________.

5. California Elementary School Science Standards for orbits
From California Science Standards, grade 5:
Students know the path of a planet around the Sun is due to the gravitational attraction between the Sun and the planet.
And from the high school standard:
Students know applying a force to an object perpendicular to the direction of its motion causes the object to change direction but not speed (e.g., Earth's gravitational force causes a satellite in a circular orbit to change direction but not speed).
Students know circular motion requires the application of a constant force directed toward the center of the circle.

6. Falling around – part 2 Are orbiting satellites falling? Yes or No?
Example: ISS: International Space Station.
Are the people inside ISS falling? Y/N?
So, ____________________________?
Draw a cartoon in your own notes that illustrates why astronauts are weightless.
Are they _______________ while in Earth orbit?

7. Universal Law of Gravity:
Newton hypothesized that _____________________ _______________________________________.
The mathematic relationship is called an Inverse Square Law and it looks like this:
Some of the questions we’re going to do in class now have been INTENTIONALLY left out of your notes.

8. Gravity is forcing you towards the person next to you.
True
False 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

9. Is there gravity on the Moon?
Yes No 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

10. Earth exerts stronger force Moon exerts stronger force
The Earth is 80x more massive than the Moon. How does the strength of the gravitational force that the Moon exerts on Earth compare to the gravitational force that Earth exerts on the Moon?
Earth exerts stronger force
Moon exerts stronger force
Forces are the same 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

11. Student debate about last question
Student 1: I thought that whenever one object exerts a force on a second object, the second object also exerts a force that is equal in strength but in the other direction. So even though Earth is bigger and more massive than the Moon, they still pull on each other with a gravitational force of the same strength, just in different directions.
Student 2: I disagree. I said that Earth exerts the stronger force because it is way bigger than the Moon. Because its mass is bigger, the gravitational force Earth exerts has to be bigger too. I think you are confusing Newton’s third law with the law of gravity

12. Who do you agree with? Student #1 Student #2 Both are right
Both are wrong
Some of each are right 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52

13. It would be four times as strong It would be twice as strong
If you were twice as far from Earth as you are now, how would gravity change?
It would be four times as strong
It would be twice as strong
It would be the same
It would be half as strong
It would be 1/4th as strong 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

14. Real triple-size planets
We just said planets that are 3x the Earth’s size have _________ gravity.
Do you think real planets that are 3x bigger than Earth have weaker gravity?
Why not?

15. If the Moon got twice as heavy, would your current weight (in this room) change noticeably?
Yes No 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

16. If the Earth’s atmosphere went away, would your weight change noticeably?
Yes No 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

17. California Elementary School Science Standards for gravity
From California Science Standards, hgih school
Students know the relationship between the universal law of gravitation and the effect of gravity on an object at the surface of Earth.

18. Masses Earth’s mass is ________________________.
_____________________________kg (__ zeroes)
____ is _____________ times heavier than a 220 lb person.
When a pen falls down, why does the pen move & the Earth doesn’t? [clicker question first].
Earth _____________________.
Similar to _____________________.  Found ____+ planets around other stars (since 1995)!

19. Which is closer to you? New York City The top of Earth’s atmosphere
They are the same distance 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

20. Gravity’s acceleration in space
Moon
To scale, ___________ ___________________.
Gravity’s acceleration in space
A previous slide showed us:
What is the ______________ in the expression above?
RHETROCIAL QUESTION: How does this affect astronauts?
How far are the astronauts from Earth?
___________________________
For a total distance of …
Has the distance changed by a big percentage?
That ________________________________________
(How high up does the atmosphere go?)
Earth

21. Summary Falling around Weightlessness
Newton’s Law of Gravity, examples
Expect questions on the next test like those we did here.