1. take ANY 2 random objects

2. take ANY 2 random objects
like an apple

3. take ANY 2 random objects
and the earth

4. take ANY 2 random objects
ignore everything else

5. See What Happens

7. WHY?
Ask students to explain what they observed. Which objects were moving? Were the objects moving at constant speeds. Show as many times as is necessary.

8. Universal Gravitation

9. that pulls any objects with mass together! the harder gravity pulls.
Verbally
Gravity is a force
that pulls any objects with mass together!
The bigger the masses
the harder it pulls.
The closer the masses
the harder gravity pulls.
Ask a student: Is there any mass in your body? Is there any mass in the ceiling? Gravity pulls masses together. Why aren’t you being pulled towards the ceiling?  the mass of the earth is a lot bigger than the mass of the cieling
Ask the class: The sun has a lot more mass than the earth. Why doesn’t student X get pulled towards the sun?  The earth is a lot closer.

10. Mathematically Fg Fg

11. Universal Gravitation
Fg: the force of gravity between object A and object B
G: the gravitational constant
mA: the mass of random object A
mB: the mass of random object B
d: the distance between object A and object B

12. Universal Gravitation
Fg: the force of gravity between object A and object B
G: the gravitational constant
mA: the mass of random object A
mB: the mass of random object B
d: the distance between object A and object B

13. Universal Gravitation
Fg: the force of gravity between object A and object B
G: the gravitational constant
mA: the mass of random object A
mB: the mass of random object B
d: the distance between object A and object B

14. Universal Gravitation
Fg: the force of gravity between object A and object B
G: the gravitational constant
mA: the mass of random object A
mB: the mass of random object B
d: the distance between the centers of objects A and object B

15. Universal Gravitation
Fg: the force of gravity between object A and object B
G: the gravitational constant
mA: the mass of random object A
mB: the mass of random object B
d: the distance between object A and object B

16. The Gravitational Constant
Your LUCKY Day!
The Gravitational Constant is
ALWAYS
the same number

17. In Case They’re Not in Your Notes Yet!
&

18. Time for an Example

19. Time for an Example
We already know:
Fg = mg
&
Now we also know:

20. Fg = mAg Time for an Example Let’s think about any random object A
then:
Fg = mAg

21. Time for an Example
Put it together with:

22. Time for an Example
And we get:

23. Luckily the mA’s cancel out:
Time for an Example
Luckily the mA’s cancel out:

24. Time for an Example
Then we’re left with:

25. If random object B is the earth:
Time for an Example
If random object B is the earth:
&
mearth = 5.98 x 1024 kg

26. Time for an Example
And if random object A

27. Time for an Example
And if random object A

28. is sitting on the earth…
Time for an Example
And if random object A
is sitting on the earth…

29. Time for an Example And if random object A is sitting on the earth…
The distance is the radius of the earth

30. is sitting on the earth…
Time for an Example
And if random object A
is sitting on the earth…
d = 6.38 x 106 m

31. Time for an Example Plug in: mearth = 5.98 x 1024 kg d = 6.38 x 106 m
G = 6.67 x 10-11

32. Time for an Example
You get:

33. Which gives us something familiar:
Time for an Example
Which gives us something familiar:

34. Universal Gravitation
Your Turn
Go get the worksheet:
Universal Gravitation
from the front table.
YOU
Get to find g on the moon.