Mass vs. Weight

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Mass vs. Weight
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Definitions

• Mass Amount of stuff (matter) in an object
• Weight Force exerted on an object because of a
  planets gravity
• Related, but not the same!
• Mass ? Weight!

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How to Find Mass

• Two types of mass!
• Gravitational Mass
• 2. Inertial Mass
• A Video

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How to Find Weight

• Weigh it!
• Calculate it!
• But how?

Like all forces, you can measure weight (force
of gravity) with a spring scale!
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Discovering the Relationship Between Mass and
Weight- OR Why Pirates Have Pet Toucans and
Not Pet Emus
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A Sample Graph(Thanks to Jacob and Teddy)
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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
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Experimental Result

• g 9.81 N/kg
• To calculate the weight, w, of an object of mass
  m
• w mg 9.81 m

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Example Calculations

• Whats the weight of a 1.2 kg toucan?
• w mg (1.2 kg)(9.81 N/kg) 11.7 N
• 2. Whats the weight of a 97 kg emu?
• w mg (97 kg)(9.81 N/kg) 952 N

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Weight Varies, Mass Does Not

• If you move to a different location, the amount
  of stuff in you doesnt change, so your mass is
  always the same.
• BUT the force of gravity may be different,
  causing your weight to be different.

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Various Values of g and Effect on Weight

• Weight on Earth
• Weight on other Planets

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A Side-by-Side Comparison
Mass Weight
Symbol m w or Fg
Unit kilogram (kg) Newton (N)
How to Determine Usually measure w mg OR w 9.8 m
Constancy Object has same mass everywhere Objects weight depends on location (planet, etc.)
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A Cheesy (but Effective) Video Comparison