Newtons laws
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Newtons laws

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Newtons laws Newtons laws Presentation Transcript

  • Newton’s Laws of Motion Red - Write it Teks: 8.6a- Demonstrate and calculate how unbalanced forces change the speed or direction of an object in motion 8.6b- differentiate between speed, velocity and acceleration Blue - Highlight it
  • 1. Motion: A change in Position
    • A. Distance vs. Displacement
    • 1. Distance: the entire path of travel OR how far you went.
    2. Displacement: the straight line measurement (distance) between starting & ending points (including direction).
  • 2. Speed vs. Velocity
    • Speed: distance traveled divided by the time needed to travel.
    • Velocity: displacement (although distance is usually used) divided by time including direction of travel.
    • Formula: s = d/t
    • Mathematically, Speed and Velocity are the SAME; Velocity adds a direction
  • 3.Graphing Speed: distance over time
    • Constant Speed (top)
      • As the time changes, the distance changes.
      • The steeper the slope, the faster the speed (more distance in less time).
      • The shallower the slope, the slower the speed (more time to cover less distance).
    • Object at rest (bottom)
      • As the time changes, the distance remains unchanged.
  • 4. Acceleration
    • Acceleration: change in velocity divided by the time needed for the change.
    • Since acceleration is a change in velocity ,
    • If you change direction, even without changing speed, you are accelerating!
    • Slowing down is also considered acceleration! It is called negative acceleration .
    • Formula: (final velocity – initial velocity)
    • time
  • 5. Graphing Acceleration: velocity over time
    • Section A: acceleration
    • Section B: no acceleration; constant velocity
    • Section C: negative acceleration
  • 6. Newton’s Laws of Motion
    • To understand Newton’s Laws:
    • Force: a push or pull with a size and direction.
      • Balanced forces: 2 forces that are equal but in opposite directions, canceling each other out.
      • Unbalanced forces: when one force is greater than another, causing a change in motion.
    • Measured in newtons, N .
  • 7. 1 st Law of Motion
    • Objects resist changes in motion!
      • If an object is at rest, it will stay at rest*
      • If an object is in motion, it will stay in motion*
        • *Unless acted on by a force!
    • Also known as: The Law of Inertia
      • More mass = more inertia
  • 8. 2 nd Law of Motion
    • An object acted on by an unbalanced force will accelerate in the direction of the force.
      • Mass (m) & Acceleration (a) affect force (F).
      • Formula: F = ma
      • When falling, acceleration is due to gravity and is a constant: 9.8 m/s 2
  • 9. 3 rd Law of Motion
    • For every action, there is an equal but opposite reaction.
      • When a force is exerted on an object, the object exerts the same amount of force.
  • 10. Force of Gravity: Mass V. Weight
    • B. Mass
      • The amount of matter an object has, regardless of any outside force being applied.
      • On the Moon, your mass would remain the same, but your weight would change.
    • C. Weight
      • The force of gravity multiplied by mass.
      • An object’s weight can change, depending on the pull of gravity.
      • On Earth, it’s calculated as mass X 9.8 m/s 2
      • Measured in Newtons.
    • Gravity: the force of attraction that exists between any two objects that have mass.
  • 11. Friction: A. a force that resists motion & is always present between 2 moving surfaces
    • Rolling friction: friction between a surface and a wheel as the wheel rolls.
    • Sliding friction: friction that occurs when 2 surfaces slide past each other, slowing down the moving object.
    • Static friction: Friction that hinders a stationary object from moving on a surface when a force is applied.
  • 12. Air Resistance: A special form of Friction
    • Why does the feather fall more slowly than the elephant?
      • Acceleration due to gravity is constant at 9.8 m/s 2 ; therefore, the elephant should hit with a stronger force, but not faster.
      • The action of air molecules ‘catch’ on the surface area of an object and slow it down.
      • According to Galileo, without air resistance, both objects would hit the ground at the same time!
  • B. Galileo proved right!
      • While on the Moon, the Apollo astronauts proved Galileo correct.
      • Although they dropped a hammer, not an elephant, the two objects landed at the same time.
    • C. Acceleration due to gravity is a constant – 9.8 m/s 2
    • Acceleration is not affected by the mass of the object!
    • (but slowing down is effected by air resistance)
  • Special note:
    • Answer to number 6 on page 22:postiive