Inertia, Mass, Weight

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Inertia, Mass, Weight
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Inertia
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Inertia
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What is Inertia?

• a property of matter.
• a measure of an objects resistance to changes in
  its motion.
• resistance to changes in speed and/or direction.
• directly proportional to an objects mass.
• more massive objects have more inertia.

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Mass and Weight

• How are they different?

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• Mass is
• the amount of matter in an object.
• a measure of the inertia of an object.
• measured in units of kilograms.
• constant everywhere.
• No matter where I take you, your mass doesnt
  change.

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Weight is

• another name for the force of gravity which the
  planet exerts on an object near its surface.
• We typically speak of our weight on Earth so we
  are talking about the force of gravity that the
  Earth exerts on us.
• a force.
• dependant on BOTH your mass and the planet which
  you are on or near.

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Out in Space

• How do you weigh an astronaut?

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Microgravityhttp//www.youtube.com/watch?vYFa8
M3fbc8c
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How to Weigh an Astronaut
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Weight Calculations

• Weight Mass (Gravitational Field Strength)
• Gravitational Field Strength depends on the
  planet and the exact location.
• On Earth, gravitational field strength g
  9.8N/kg.
• In other words, the earth exerts 9.8N of force on
  you for every 1 kg of mass.
• On Earth,
• Weight (in Newtons) Mass (in kilograms)
  9.8N/kg

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English versus Metric Units
Metric Units English Units
Mass Kilograms Slugs
Weight Newtons Pounds (lbs)
Note 9.8 Newtons 2.2 lbs
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Question 1

• Determine the weight (in Newtons) of a 64 kg
  object on planet Earth.

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Question 2

• Determine the mass (in kilograms) of an object
  which weighs 200 N on planet earth.

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