Free Fall

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Free Fall

• At the surface of the earth, the force of gravity
  on any object depends directly on the mass of the
  object.
• That is why more massive objects weigh more
• Lets explore what this means

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Free Fall
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Free Fall

• Accurate close to the surface of the earth
• To simplify any problems we will work, we neglect
  air resistance (physicists are lazy!)
• g actually changes as we move to higher altitudes
  (well see why later)

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Forces are Interactions

• We talked about the four fundamental forces
• Interaction between objects

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Newtons Third Law of Motion

• Whenever one object exerts a force on a second
  object, the second object exerts an equal and
  opposite force on the first.
• To every action there is always an opposed equal
  reaction.
• Interactions occur in pairs

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Newtons Third Law of Motion
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Effect of Different Masses
Forces the same, accelerations are different!!!!
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Vectors and Scalars

• Scalars have size
• Mass, speed, volume, temperature
• Vectors have size and direction
• Velocity, acceleration, force

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Adding Vectors
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Example of Force Vectors
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Example of Force Vectors
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Example of Force Vectors
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Example of Velocity Vectors
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Components of Vectors
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Components of Vectors
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Momentum Defined

• Easier to stop a compact car than a Greyhound bus
• Bus has more MOMENTUM
• Momentum mass X velocity
• Momentum mv

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Impulse Defined

• Forces change motion, so velocity changes
• If velocity changes, momentum changes
• Amount of momentum change depends on how long we
  apply the force
• Impulse force X time

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Impulse and Momentum Related
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Conservation of Momentum

• In the absence of an external force, the
  momentum of a system remains unchanged.
• When a quantity doesnt change, we say it is
  conserved
• Very deep meaning, connected with the idea that
  the Laws of Physics are unchanged if you move to
  a new location

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Elastic Collisions
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Inelastic Collisions