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Equilibrium

Equilibrium. Things not Moving (sweet). Everyday Forces. Weight : This is the force of gravity. Or gravity acting on a mass w = mg 2. Normal Force : The force a surface applies to an object. It is ALWAYS perpendicular to surface. Everyday forces cont.

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Equilibrium

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  1. Equilibrium Things not Moving (sweet)

  2. Everyday Forces • Weight: This is the force of gravity. Or gravity acting on a mass w = mg 2. Normal Force: The force a surface applies to an object. It is ALWAYS perpendicular to surface

  3. Everyday forces cont. • Tension: The force applied by a rope. Or the force in a rope. Ropes only pull. • Applied Force: A force applied by some object, like a person, that does not fall into any previous category • Friction: The force a surface applies that resists motion or an applied force

  4. Drawing Free Body Diagrams • Draw forces acting on object acting through the center of mass • Label “everyday” Forces FN mg

  5. Forces in Equilibrium • ΣF = 0meaning: ΣFx = 0 ΣFy = 0 ΣFz = 0

  6. Forces in Equilibrium (ex 5.3 p. 157)

  7. Forces in Equilibrium F = ? 12 N 16 N @ 68° Θ = ? 60° 25 N

  8. Objects in Equilibrium • All the forces on an object must add to zero for the forces to be in equilibrium, however this is just the first condition for an object to be in equilibrium. • You see, in addition to the object’s center of mass having no acceleration, we also want the object to not rotate

  9. 2nd Condition for Equilibrium

  10. Torque • A force applied to an object away from a pivot point (let’s say a distance r) will cause the object to rotate (think of a door or wrench). • A torque is the measure of the tendency of a force to cause or change the rotational motion of a body

  11. Torque • Counterclockwise rotations will be POSITIVE • Clockwise rotations will be NEGATIVE (your book arbitrarily chose this)

  12. Center of Gravity

  13. What is m?

  14. Example 11.2 p 410

  15. Example 11.3 p 411

  16. Classic Situations • Diving Board (#11 p. 426) • Sign (#13, 14 p. 426) • Door (on board) • Ladder (#10 p. 426) • No torque hanging chandelier (# 7, 8 p194)

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