Forces

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Forces

• Contact Forces

• Non-Contact Forces

• Friction
• Applied
• Normal
• Tension
• Spring Force

• Gravity
• Electricity
• Magnetism

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Gravity

• Force that pulls objects toward each other
• Law of Universal Gravitation
• The force of gravity acts between all objects in
  the universe that have mass.
• We are attracted toward Earth and Earth is
  attracted towards us.
• our mass is very small

3
Factors affecting Gravity

• Mass
• More mass stronger the gravitational pull
• Weight is greater on Jupiter than on Earth
• Distance
• Greater distance less force

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4
Friction

• Friction is a force that opposes motion between
  two surfaces that are in contact.
• When two surfaces are in contact, the microscopic
  hills and valleys of one surface stick to the
  tiny hills and valleys of the other surface. This
  contact causes friction.

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friction

• Two factors that affect the force of friction are
  the types of surfaces involved and how hard they
  are pushed together.
• The rougher the surface the greater the force
• Sandpaper vs. Ice
• The heavier the object the greater the force of
  friction.
• The harder the surfaces are pushed together, the
  stronger the force of friction.

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Friction Friend or Foe?

• With your table partner, discuss these four
  questions and come up with a list of at least
  three answers per question. Be ready to share
  with the class.
• In what ways is friction helpful in the world?
• In what ways is friction harmful?
• What are some ways to reduce friction?
• What are some ways to increase friction?

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Friend and foe

• Friction can be both harmful and helpful, so it
  may be necessary to decrease or increase
  friction.

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Friction

• Increases

• Decreases

• Rougher surface
• Sand, gravel on ice
• Increase the applied force
• Use force when sanding

• Lubricants
• Oil, wax, grease
• Rolling
• Ball bearings
• Smoother surface