1. Mass vs Weight

2. Mass = the amount of matter in an object
Matter = the substance that all physical objects are made of
Matter is anything that has mass and takes up space
Mass = the amount of matter in an object

3. Mass
Finding the mass is equivalent to counting the number of atoms (amount of matter) something is made of

4. Mass
We can’t really count atoms, instead we compare objects by using a balance
If a bowling ball has a mass of 1000g, that’s like saying it has the same number of atoms as 1000g of water or 1000g of gold or 1000g of chips!

5. Isaac Newton
1642 – 1727

6. Not only does each atom have mass, it also has inertia
Inertia = a resistance to a change in motion

7. A moving bowling ball will just keep going until some force stops it
Mass
A bowling ball will stay in one place forever, until some force pushes or pulls it.
A moving bowling ball will just keep going until some force stops it

8. Mass A bowling ball has more atoms A bowling ball has more inertia
Would you rather have a catch with a bowling ball or a soccer ball?
A bowling ball has more atoms
A bowling ball has more inertia
A bowling ball is harder to throw and to catch

9. Isaac Newton
1642 – 1727

10. What strange force makes an apple (or anything else) fall from a tree?
GRAVITY

11. Newton theorized that all matter has gravity
An invisible force that attracts all matter to all other matter

12. What determines the amount of gravity?

13. mass = the amount of atoms in an object
What determines the amount of gravity?
If every atom has gravity, then more atoms means more gravity
mass
= the amount of atoms in an object

14. What determines the amount of gravity?
Which has more mass, an apple or a chimp?
Which has more mass, the apple or the Earth?
Which has more gravity between them, an apple and a chimp or the apple and the Earth?

15. What determines the amount of gravity?
Which has more mass, the Earth or the Sun?
Which has more gravity between them, an apple and the Earth or an apple and the sun?
The Sun obviously has more mass and more gravity, then how can the Earth pull harder?
There must be more than just mass involved!

16. What determines the amount of gravity?
Newton decided that the farther away you get, the weaker gravity becomes.

17. What determines the amount of gravity?
Mass
Distance

18. What determines the amount of gravity?
Newton actually found a way to quantify the amount of gravity

19. Law of gravity

20. Law of gravity
Notice you need the mass of BOTH objects
ALSO – it is the distance between objects, NOT the distance from the Earth
Notice it is distance SQUARED.
2x the distance = 4x weaker gravity
3x the distance = 9x weaker gravity
10x the distance = 100x weaker gravity

21. What would gravity be like on the moon?
Gravity depends on the mass and the distance between objects.
Say you weigh 120 lbs on Earth, then travel to the moon.
The Moon is approximately 1/6 of the mass of the Earth. (Would your mass change?)

22. Things DO NOT float on the moon!
What would gravity be like on the moon?
1/6 the mass will mean 1/6 the gravity!!!!
Things DO NOT float on the moon!
Things weigh 6x less and fall 6x slower!
The Moon is approximately 1/6 of the mass of the Earth.

23. MASS = the amount of atoms Weight = the amount of gravity
So what is the actual difference between mass and weight?
MASS = the amount of atoms
Weight = the amount of gravity
On the moon
Mass is the same, weight 6x less

24. Flying in an airplane Mass is the same, gravity is slightly weaker
So what is the actual difference between mass and weight?
Deep in a coal mine Mass is the same, gravity is slightly larger
Flying in an airplane Mass is the same, gravity is slightly weaker

25. Mars is about 80% the mass of Earth. What would you weigh on Mars?

26. Explain this !!!!

27. A spring scale is used to measure weight
PAY ATTENTION to the pointer when you zero the scale!

29. Universal Gravitational constant
6.67 x m3 kg-1 s-2 OR m3
kg s2