Statics is the branch of physics dealing with objects in equilibrium' It includes:

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Statics

• Statics is the branch of physics dealing with
  objects in equilibrium. It includes
• center of gravity
• torque
• translational and rotational equilibrium

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Center of Gravity

• Center of Gravity -
• point located at an objects average position of
  weight. For a symmetrical object made of a
  single material, this is at the geometric center.

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Center of Gravity

• Center of Gravity -
• the effect of gravity on an object can be treated
  as a single force acting through the objects
  center of gravity.
• if you suspend an object and it is free to move,
  the center of gravity will always wind up below
  the suspension point.

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Center of Gravity

• Center of Mass -
• Average position of all the particles of mass
  that make up an object.
• Only rarely is the center of mass different from
  the center of gravity (tall buildings).

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Center of Gravity

• Center of Gravity Examples -
• bowling ball basketball donut
• filing cabinet ruler pot
• bookshelf chair bat
• empty plane full plane man
• empty ship full ship woman

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Center of Gravity

• Stability and tipping over -
• When a line drawn from the center of gravity of
  an object in the direction of the gravitational
  force lies outside of the supporting base, the
  object is unstable and will tip over to find a
  stable position.

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Center of Gravity

• Stability and tipping over -
• If any movement causes a balanced object to raise
  its center of gravity, that object is in stable
  equilibrium.
• If any movement causes a balanced object to lower
  its center of gravity, that object is in unstable
  equilibrium.

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Center of Gravity
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Center of Gravity
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Torque

• Torque -
• the turning action of a force about an axis or
  pivot point. Also called the moment of a force.
• torque increases if the force increases or the
  distance of the force to the axis of action
  increases.

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Torque

• Torque -
• force times the perpendicular distance from the
  axis of rotation.
• F?d (sin?)
• units are N?m (newton meters)

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Torque

• Torque Examples -
• wrench pulley faucet
• screwdriver ax arm
• car wheel door leg
• steering wheel door knob

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Torque

• Torque and rotational equilibrium -
• the net torque acting on an object about any axis
  is zero.
• Reminder the first condition of equilibrium is
  that the net force acting on an object is zero.

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Torque

• Torque and equilibrium -
• S? 0
• and
• SF 0

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Center of Gravity

• Finding Center of Gravity -
• the torque acting on the center of gravity of an
  object can be equated to the sum of the
  individual torques.
• (m1g m2g )xCG (m1gx1 m2gx2 )

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Center of Gravity

• Finding Center of Gravity -
• solving for xCG
• xCG (m1gx1 m2gx2 )
• (m1g m2g )

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Center of Gravity

• Finding Center of Gravity -
• solving for xCG
• xCG Smixi and yCG Smiyi
• Smi Smi

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Statics

• END OF STATICS

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Statics

• Notes