Section 2.1 Forces change motion

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Section 2.1 Forces change motion

• Mrs. Leos
• Eighth Grade Science

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Forces

• A push or a pull
• Three types
• Contact Force
• When objects use force by pushing or pulling an
  object.
• Gravity
• Friction

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Vectors

• A quantity that measures both size and direction
• Force is a vector
• Direction of arrow is direction of force
• Size of arrow is size of force (bigger arrow
  more force, smaller arrow less force)
• What other kind of vector have you already
  learned about?

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Net Force

• Overall force acting on an object when all the
  forces are combined.
• Total force that affects an object when multiple
  forces are combined.
• The net force depends on both the direction and
  the size of individual forces.

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Balanced Forces
Unbalanced Forces

• Object does not move
• No net force
• Same effect as no force
• Also act on object moving in straight line with
  constant velocity

• Object moves
• Net force in one direction
• One force on an object is greater than another

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Measuring Net Force

1. Identify forces to combine.
2. Put tail of second force arrow to tip of first.
   Maintain size and direction
3. Measure from tail of first arrow to tip of second
   force arrow.

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Combining forces in opposite directions
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Combining forces in the same direction
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Newtons First Law

• Objects at rest remain at rest, and objects in
  motion remain in motion with the same velocity,
  unless acted upon by an unbalanced force
• Objects with no net force acting on them have
  either constant velocity or zero velocity
• Force is needed to start, change, or stop motion

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Inertia

• Resistance of an object to a change in motion
• Directly related to an objects mass