1. Mass vs. Weight

2. Related, but not the same!
Definitions
Mass – Amount of stuff (matter) in an object
Weight – Force exerted on an object because of a planet’s gravity
Related, but not the same!
Mass ≠ Weight!

3. How to Find Mass Two types of mass! Gravitational Mass
2. Inertial Mass
A Video

4. How to Find Weight Weigh it! Calculate it! But how?
Like all forces, you can measure weight
(force of gravity) with a spring scale!

5. Discovering the Relationship Between Mass and Weight - OR – Why Pirates Have Pet Toucans and Not Pet Emus
Arg?

6. A Sample Graph (Thanks to Jacob and Teddy)

7. The Importance of the Slope
Tells you how much the weight (Fg) varies with mass: If you increase the mass by 1 kg, how much do you increase the weight by?
Our calculated slopes

8. g = 9.81 N/kg w = m∙g = 9.81 ∙ m Experimental Result
To calculate the weight, w, of an object of mass m:
w = m∙g = 9.81 ∙ m

9. Example Calculations What’s the weight of a 1.2 kg toucan?
w = mg = (1.2 kg)(9.81 N/kg) = 11.7 N
2. What’s the weight of a 97 kg emu?
w = mg = (97 kg)(9.81 N/kg) = 952 N

10. Weight Varies, Mass Does Not
If you move to a different location, the amount of stuff in you doesn’t change, so your mass is always the same.
BUT the force of gravity may be different, causing your weight to be different.

11. Various Values of g and Effect on Weight
Weight on Earth
Weight on other Planets

12. A Side-by-Side Comparison
Mass
Weight
Symbol m
w or Fg
Unit
kilogram (kg)
Newton (N)
How to Determine
Usually measure
w = m∙g OR
w = 9.8 ∙m
Constancy
Object has same mass everywhere
Object’s weight depends on location (planet, etc.)

13. A Cheesy (but Effective) Video Comparison