Describing Motion Newton’s Laws
First we need to define the word  FORCE : <ul><li>The cause of motion (what causes objects to move) </li></ul><ul><li>Two ...
Forces are measured in  Newtons <ul><li>SI unit of force </li></ul><ul><li>Symbol: N </li></ul><ul><li>Measured by using a...
Forces may be  balanced  or  unbalanced <ul><li>Balanced forces  – all forces acting on an object are equal </li></ul><ul>...
Newton’s Laws <ul><li>First Law – Inertia   </li></ul><ul><li>Second Law – Acceleration, Force & Mass  </li></ul><ul><li>T...
First Law <ul><li>Inertia </li></ul><ul><ul><li>An object  at rest  [not moving] remains at rest unless acted on by a forc...
First Law <ul><li>Inertia & Mass </li></ul><ul><ul><li>Mass  is the amount of matter in an object </li></ul></ul><ul><ul><...
Second Law <ul><li>Acceleration & Mass Definitions </li></ul><ul><ul><li>Acceleration  is a change in velocity [speed or d...
Second Law <ul><li>Acceleration & Force </li></ul><ul><ul><li>The more  force  placed on  an object, the more it will  acc...
Third Law <ul><li>Action – Reaction </li></ul><ul><ul><li>Forces are always produced in  pairs  with  opposite  directions...
The truck is  in motion .  What is the  force  that causes it to stop?  The  push  of the stopped car. The car is  at rest...
What about the ladder on top of the truck? The ladder is in motion because the truck is in motion. When the truck stops, t...
The truck is  in motion , the car is  at rest .  How do each of these vehicles  accelerate ? The truck stops moving.  The ...
Why does the car  move  [accelerate] when it is hit by the truck? The heavy and moving truck has  more force  than the sma...
The truck hits the car.  An  action force  stops the truck. What is the  equal and opposite  reaction force? The force tha...
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Newton's Laws of Motion

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Newton's Laws of Motion

  1. 1. Describing Motion Newton’s Laws
  2. 2. First we need to define the word FORCE : <ul><li>The cause of motion (what causes objects to move) </li></ul><ul><li>Two types of forces </li></ul><ul><ul><li>Pushes </li></ul></ul><ul><ul><li>Pulls </li></ul></ul>
  3. 3. Forces are measured in Newtons <ul><li>SI unit of force </li></ul><ul><li>Symbol: N </li></ul><ul><li>Measured by using a spring scale </li></ul>
  4. 4. Forces may be balanced or unbalanced <ul><li>Balanced forces – all forces acting on an object are equal </li></ul><ul><ul><li>There is NO MOTION </li></ul></ul><ul><li>Unbalanced forces – one or more forces acting on an object are stronger than others </li></ul><ul><ul><li>There is MOTION </li></ul></ul><ul><ul><ul><li>A NET FORCE </li></ul></ul></ul>
  5. 5. Newton’s Laws <ul><li>First Law – Inertia </li></ul><ul><li>Second Law – Acceleration, Force & Mass </li></ul><ul><li>Third Law – Action-Reaction </li></ul>
  6. 6. First Law <ul><li>Inertia </li></ul><ul><ul><li>An object at rest [not moving] remains at rest unless acted on by a force [push or pull] </li></ul></ul><ul><ul><li>An object in motion remains in motion unless acted on by a force [push or pull] </li></ul></ul>
  7. 7. First Law <ul><li>Inertia & Mass </li></ul><ul><ul><li>Mass is the amount of matter in an object </li></ul></ul><ul><ul><li>The more MASS an object has, the more INERTIA the object has. </li></ul></ul><ul><ul><li>Bigger objects are harder to start & stop </li></ul></ul>http://toons.artie.com
  8. 8. Second Law <ul><li>Acceleration & Mass Definitions </li></ul><ul><ul><li>Acceleration is a change in velocity [speed or direction] </li></ul></ul><ul><ul><li>Mass is the amount of matter in an object </li></ul></ul>
  9. 9. Second Law <ul><li>Acceleration & Force </li></ul><ul><ul><li>The more force placed on an object, the more it will accelerate [change its motion] </li></ul></ul><ul><li>Acceleration & Mass </li></ul><ul><ul><li>The more mass [or inertia ] an object has, the more force it takes to accelerate the object </li></ul></ul>
  10. 10. Third Law <ul><li>Action – Reaction </li></ul><ul><ul><li>Forces are always produced in pairs with opposite directions & equal strengths </li></ul></ul><ul><ul><li>For every force there is an equal and opposite force </li></ul></ul>
  11. 11. The truck is in motion . What is the force that causes it to stop? The push of the stopped car. The car is at rest . What is the force that causes it to move? The push of the truck.
  12. 12. What about the ladder on top of the truck? The ladder is in motion because the truck is in motion. When the truck stops, the ladder stays in motion. The truck is stopped by the force of the car, but the ladder is not. What force stops the ladder? Gravity .
  13. 13. The truck is in motion , the car is at rest . How do each of these vehicles accelerate ? The truck stops moving. The car starts moving. Which one will be the hardest to accelerate ? The truck because it has the most mass.
  14. 14. Why does the car move [accelerate] when it is hit by the truck? The heavy and moving truck has more force than the small, at rest car. Why does the truck stop moving when it hits the car? The force of the car pushing back on the truck, plus the force of friction between the massive truck and the road slow down, the stop the truck.
  15. 15. The truck hits the car. An action force stops the truck. What is the equal and opposite reaction force? The force that pushes the car forward.

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