mass vs. weight. definitions mass – amount of stuff (matter) in an object weight – force exerted...
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Mass vs. Weight
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!
How to Find Mass
Two types of mass!• Gravitational Mass
2. Inertial Mass
A Video
How to Find Weight1. Weigh it!
2. Calculate it!
But how?
Like all forces, you can measure weight (force of gravity) with a spring scale!
Discovering the Relationship Between Mass and Weight
- OR –Why Pirates Have Pet Toucans
and Not Pet EmusArg?
A Sample Graph(Thanks to Jacob and Teddy)
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
Experimental Result
g = 9.81 N/kg
To calculate the weight, w, of an object of mass m:
w = m∙g = 9.81 ∙ m
Example Calculations
1. 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
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.
Various Values of g and Effect on Weight
Weight on Earth
Weight on other Planets
A Side-by-Side ComparisonMass 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.)
A Cheesy (but Effective) Video Comparison
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