Friction, Gravity, and Elastic Forces Section 10.2 Page 380

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Friction, Gravity, and Elastic ForcesSection
10.2Page 380
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Objectives for 10.2

• Identify the two factors that will determine the
  friction force between two objects.
• Identify the two factors that affect the
  gravitational force between two objects.
• Be able to draw a force diagram of all forces
  acting on an object.
• Explain why objects accelerate during free fall.
• Explain when matter is considered to be elastic.

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Friction

• Friction The force that one surface exerts on
  another when the two rub against each other.
• Friction acts in the opposite direction of an
  objects movement.
• Friction opposes motion and can eventually cause
  an object to stop.
• The strength of friction depends on
• 1. The type of surfaces involved
• 2. How hard the surfaces push together

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Sometimes FRICTION can be a positive thing
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Sometimes FRICTION can be a negative thing
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• What are some instances when FRICTION is a
  positive thing?
• What are some instances when FRICTION is a
  negative thing?

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Types of Friction

• Static Friction
• Friction that acts on objects to prevent them
  from moving

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Types of Friction

• Sliding Friction
• Friction that occurs when two surfaces slide over
  each other

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Types of Friction

• Rolling Friction
• Friction that occurs when an object rolls across
  a surface

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Types of Friction

• Fluid Friction
• Friction that occurs when a solid object moves
  through a fluid.
• What is a fluid?

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Gravity

• Gravity a force that pulls objects toward each
  other
• Since it acts everywhere, this law is called the
  Law of Universal Gravitation
• Any two objects anywhere in the universe attract
  each other

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Gravity

• The force of gravity between objects depends on
• The mass of the objects
• The distance between the objects
• The force of gravity between objects increases
  with greater mass and decreases with greater
  distance

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Gravity
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Mass vs. Weight

• Mass the amount of matter in an object.
• A jar of nails has more mass than a jar of cotton
  balls.
• The SI unit for mass is grams.
• Weight the amount of gravitational force
  exerted on an object
• Weight Mass X Acceleration due to gravity

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Gravity and Motion

• Free Fall --- When the force of gravity alone is
  acting on an object. (not considering any wind
  resistance)
• What will fall fastest an object of greater mass
  or lesser mass?

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Gravity and Motion

• Air Resistance --- A type of fluid friction
  caused by objects bumping into molecules in the
  air.

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Gravity and Motion

• Projectile Motion --- Motion from throwing an
  object with both a horizontal velocity and an
  acceleration vertically due to gravity

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Gravity and MotionProjectile motion
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Projectile Motion
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Elastic Forces

• Matter is considered elastic, IF
• it returns to its original shape after it is
  squeezed or stretched.

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Compression

• Compression is an elastic force that squeezes or
  pushes matter together

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Tension

• Tension is an elastic force that stretches or
  pulls matter

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Compression and TensionElastic Forces
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