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Equilibrium

Equilibrium. Force is A push or pull on an object. A vector with magnitude and direction. Force is not Energy. Power. Momentum. Velocity. Force. Fundamental Forces. Gravity is a fundamental force. It acts upon objects from a distance away from the source (such as the Earth).

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Equilibrium

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  1. Equilibrium

  2. Force is A push or pull on an object. A vector with magnitude and direction. Force is not Energy. Power. Momentum. Velocity. Force

  3. Fundamental Forces • Gravity is a fundamental force. • It acts upon objects from a distance away from the source (such as the Earth). • There are two other fundamental forces. • Electroweak force is common in everyday life. • Electricity • Magnetism • Light • Radioactive decay • Nuclear force is uncommon in everyday life. • Nuclear fission (nuclear power plants) • Nuclear fusion (stars)

  4. Contact Forces • Many forces are due to contact between objects. • Kick a ball • Push with a bulldozer • Tug from a rope • Friction due to the ground • The actual force is electricity, but the atoms are so small we can treat the forces as coming from contact by larger objects.

  5. Newton’s Laws • Ancient scientists looked to the natural properties of objects. • Motion was a result of the object’s properties. • Newton defined motion based on forces acting from outside an object. • Motion was the result of external forces. • Three laws were used to define the behavior of forces on objects.

  6. First Law: Law of Inertia • An object continues at rest, or in uniform motion in a straight line, unless a force is imposed on it. • This describes constant velocity, including zero. • No change means no force, and vice versa. no force rocket constant velocity

  7. Zero Net Force • An object at rest with no net force is in static equilibrium. • The net force is due to the sum of forces acting on the object. • The forces are vectors

  8. An advertising sign weighs 210 N. It is supported from a post with a horizontal beam, and by a chain making an angle of 35 from the horizontal. What is the force in the chain? Static Forces q = 35º Newton Legal W = 210 N

  9. With no motion, forces must sum to zero. Identify forces on the sign. C is the force on the chain B is the force on the beam W is the weight Vector sum is zero. Vector Forces

  10. To find the values, use components Find the vertical components for the force on the chain. Cy = C sinq Wy = -210 N 0 = Cy + Wy= C sinq + Wy C = -Wy / sinq = 370 N Use horizontal components for the force on the beam. 0 = Bx + Cx = Bx+ (-C cosq) Bx = C cosq = 300 N Force Components Cy q = 35º Bx Cx Wy = -210 N

  11. Constant Velocity • Constant velocity means no change in motion. • Dynamic equilibrium applies in states of constant, non-zero velocity. • Zero net force used here: • FN + Fg + Fy = 0 • Fx + Ffr = 0 v0 FN Ffr Fx Fg Fy next

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