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All About Forces

All About Forces. http://www.youtube.com/watch?v=HK8afQRrOck. Forces . General Characteristics: They are vectors Push or Pull Units = Newtons , Pounds Newton = force required to accelerate 1 kg at a rate of 1 m/s ². Nature of Forces.

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All About Forces

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  1. All About Forces http://www.youtube.com/watch?v=HK8afQRrOck

  2. Forces General Characteristics: • They are vectors • Push or Pull • Units = Newtons, Pounds • Newton = force required to accelerate 1 kg at a rate of 1 m/s²

  3. Nature of Forces • Forces exist in pairs (its impossible for a single force to act on an object) • Forces arise as a result of actions / reactions between objects • There are always forces acting on all objects • ***There are 4 fundamental forces** • Gravitational, electromagnetic, strong nuclear, weak nuclear

  4. Classification Of ForcesContact & Long-Range & Short Range • Contact: • Frictional Force • Applied Force • Normal Force • Tension Force • Long Range: • Gravitational • Electromagnetic • Short Range: • Strong Nuclear • Weak Nuclear

  5. Gravitational Force • Weakest of all forces • Only noticed when one object is massive • Acts over infinite distances

  6. Electromagnetic Force • Can be repulsive or attractive • Acts between objects with an electrical charge • Holds atoms and molecules together

  7. Strong Nuclear Force • Strongest of all forces • Only acts over distances comparable to the size of an atom • The force that holds protons and neutrons together

  8. Weak Nuclear Force • Also acts over small distances • Involved in radioactive decay We will study gravitational & electromagnetic forces later on…

  9. Drawing Free Body Diagrams • A book is at rest on a tabletop.

  10. Drawing Free Body Diagrams • A girl is suspended motionless from the ceiling by two ropes.

  11. Drawing Free Body Diagrams • An egg is free-falling from a nest in a tree. Neglect air resistance.

  12. Drawing Free Body Diagrams • A rightward force is applied to a book in order to move it across a desk with a rightward acceleration. Consider frictional forces. Neglect air resistance.

  13. Drawing Free Body Diagrams • A car is coasting to the right and slowing down.

  14. Drawing Free Body Diagrams • A force is applied to the right to drag a sled across loosely packed snow with a rightward acceleration.

  15. Newton’s 3 Laws of Motion • #1 = Objects at rest stay at rest, objects in motion stay in motion (unless acted on by an outside force). • Inertia • Tendency of an object to resist change • http://www.youtube.com/watch?v=--MDILG7Znk

  16. Net Force and Equilibrium • The net force is the vector sum of all the forces that act upon an object • When forces are Unbalanced • Equilibrium • If the net force on an object is Zero • Object is either at rest or a constant velocity

  17. Determine the missing forces

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