Newtons Laws Of Motion2008

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Newtons Laws Of Motion2008

  1. 1. Notes: Newton’s Laws of Motion CW: Action-Reaction Forces
  2. 2. Newton’s Laws of Motion March 18, 2009
  3. 3. Objectives <ul><li>Explain the three laws of motion </li></ul>
  4. 4. 1 st Law of Motion (Law of Inertia) <ul><li>An object at rest will stay at rest, and an object in motion will stay in motion traveling in a straight line, unless acted upon by an unbalanced force. </li></ul>
  5. 5. 1 st Law <ul><li>Once in motion, unless acted on by an unbalanced force it would never stop! </li></ul>
  6. 6. 1 st Law <ul><li>Unless acted upon by an unbalanced force, this golf ball would sit on the tee forever. </li></ul>
  7. 7. Because of inertia, objects resist changes in their motion. When the car going 80 km/h is stopped by the brick wall, your body keeps moving at 80 km/h. Wear a seatbelt!
  8. 8. <ul><li>Why then, do we observe every day objects in motion slowing down and becoming motionless seemingly without an outside force? </li></ul>
  9. 9. <ul><li>There are four main types of friction: </li></ul><ul><ul><li>Sliding friction: ice skating </li></ul></ul><ul><ul><li>Rolling friction: bowling </li></ul></ul><ul><ul><li>Fluid friction: air or water resistance </li></ul></ul><ul><ul><li>Static friction: initial friction when moving an object </li></ul></ul>Friction!
  10. 10. 2 nd Law F = m x a
  11. 11. 2 nd Law <ul><li>The net force of an object is equal to the product of its mass and acceleration, or F=ma. </li></ul>
  12. 12. 2 nd Law <ul><li>The unit of force is in newtons (N). </li></ul><ul><li>One N is equal to the force required to accelerate one kg of mass at one m/s/s. </li></ul>
  13. 13. Newton’s 2 nd Law proves that different masses accelerate to the earth at the same rate, but with different forces. <ul><li>We know that objects with different masses accelerate to the ground at the same rate. </li></ul><ul><li>However, because of the 2 nd Law we know that they don’t hit the ground with the same force. </li></ul>F = ma 98 N = 10 kg x 9.8 m/s/s F = ma 9.8 N = 1 kg x 9.8 m/s/s
  14. 14. 3 rd Law <ul><li>For every action, there is an equal and opposite reaction. </li></ul><ul><li>Forces always act in pairs </li></ul>
  15. 15. Newton’s 3rd Law in Nature <ul><li>A fish uses its fins to push water backwards. The water reacts by pushing the fish forwards, propelling the fish through the water. </li></ul>
  16. 16. 3 rd Law As the birds push down on the air with their wings, the air pushes their wings up and gives them lift.
  17. 17. Action-reaction force pairs make it possible for birds to fly.
  18. 18. Other examples of Newton’s Third Law <ul><li>The baseball forces the bat to the left (an action); the bat forces the ball to the right (the reaction). </li></ul>
  19. 19. 3 rd Law Various fuels are burned in the engine, producing hot gases. As the gases move downward, the rocket moves in the opposite direction.

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