example: if a car stops suddenly inertia causes you to cont

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NEWTONS LAWS
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FORCE

• Force The push or pull on an object
• Net Force The overall force on an object
• Unbalanced force When there is a net force that
  causes acceleration
• Balanced forces Equal forces acting in opposite
  directions that will not change an objects motion

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Examples of Force
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MODELING FORCE
UNBALANCED FORCES
BALANCED FORCES
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MODELING FORCE
UNBALANCED FORCES IN THE SAME DIRECTION
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PICTURING BALANCED FORCES
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PICTURING UNBALANCED FORCES
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Friction

• The force that one surface exerts on another when
  the two objects rub against each other
• Friction acts in a direction opposite the
  objects direction of motion.
• Without friction an object would continue to move
  at a constant speed forever

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Factors and Friction

• The strength of friction depends on two factors
• The type of surfaces involved
• How hard the surfaces push together
• Rough surfaces produce greater friction than
  smother surfaces

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Sliding Friction

• Sliding friction - when two solid surfaces slide
  over each other.
• A snowboarder slides over the snow covered slopes
  using sliding friction everyday.

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Rolling Friction

• Rolling friction - when an object rolls over a
  surface.
• Skate boarders take advantage of this type of
  friction all the time. Reducing the amount of
  friction between the surface and the wheels allow
  skaters to go really fast.

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Fluid Friction

• Fluid friction - when an object moves through a
  fluid.
• This is how a surfer glides over the water or a
  shark glides through the water. This type is
  called fluid friction.

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NEWTONS FIRST LAW OF MOTION

• An object at rest will remain at rest and an
  object in motion will remain in motion unless
  acted upon by some outside force

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Inertia

• Inertia is the resistance to change in motion
• EXAMPLE If a car stops suddenly inertia causes
  you to continue moving forward. In order for
  change in motion to occur a force is required,
  such as a seat belt or the windshield

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Mass

• The amount of matter in an object
• EXAMPLE A jar of pennies has more mass than a
  jar of feathers
• The amount of inertia on an object depends on the
  objects mass
• The greater the mass, the greater its inertia

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NEWTONS SECOND LAW OF MOTION

• The net force of an object is equal to the
  product of its acceleration and mass
• FORCE MASS x ACCELERATION
• UNITS kg m/s² NEWTON (N)

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PRACTICE THE SECOND LAW

• A 53kg water-skier is being pulled by a
  speedboat. The force causes her to accelerate at
  2m/s². Calculate the force.
• Force mass x acceleration
• Force 52kg x 2m/s²
• Force 104 N

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LETS PRACTICE AGAIN

• What force is needed to accelerate an object with
  a mass of 25000 grams at a rate of 10 m/s2?
• Convert grams to kilograms
• 25000 g 25 kg
• Force 25 kg x 10 m/s2
• Force 250 N

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LETS TRY ANOTHER ONE

• What is the force on a 1,000 kg elevator
  accelerating at 2 m/s²?
• Force 1000kg x 2 m/s²
• Force 2000 N

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SOLVING FOR ACCELERATION

• You can use force to find acceleration
• Acceleration force/mass
• You can increase acceleration by change force
• Increase force increase acceleration
• Increase mass decrease acceleration

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LETS FIND ACCELERATION

• A 825N force is exerted on a 55kg cart. Find the
  carts acceleration.
• Acceleration force/mass
• Acceleration 825N / 55kg
• Acceleration 15 m/s²

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NEWTONS THIRD LAW OF MOTION

• For every action there is an equal but opposite
  reaction

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Example of the 3rd Law
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Momentum

• Momentum is the product of its mass and velocity
• The more momentum an object has the harder it is
  to stop
• Momentum mass x velocity
• Unit kg m/s

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Lets Practice

• Which has more momentum a 3kg sledgehammer swung
  at 1.5 m/s or a 4 kg sledgehammer swung at 0.9
  m/s
• Momentum mass x veloctity
• Momentum1 3 kg x 1.5 m/s
• Momentum1 4.5 kgm/s
• Momentum2 4 kg x 0.9 m/s
• Momentum2 3.6 kgm/s

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Conservation of Momentum

• Lw of Conservation of Momentum states that the
  total momentum of the objects that interact does
  not change.
• The total momentum remains the same unless acted
  upon by an outside force

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Momentum- 2 moving objects

• When a car bumps into another car that is going
  slower, it transfers its momentum into the other
  car.
• The car that got bumped is now going faster,
  while the car that hit it is going slower

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Momentum- 1 object moving

• If a moving objects hits a nonmoving object all
  the momentum is transferred. The nonmoving
  object begins to move and the moving object stops.

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Gravity

• Gravity-The force that pulls objects towards to
  Earth.
• Free fall When gravity is the only force acting
  on an object
• Objects in free fall accelerate as they move
  towards the Earth.

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Terminal Velocity

• Terminal Velocity is the greatest velocity an
  object can reach will falling

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Gravity

• Near the Earths surface the rate of acceleration
  due to gravity is 9.8 m/s²
• This does not take into account friction
• All objects will accelerate down at the same rate
  regardless of mass
• A brick and a feather will hit the ground at the
  same time if it were inside an airless chamber
  (vacuum)

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Projectile versus free fall

• An object thrown and an object dropped will both
  free fall at a rate of 9.8 m/s²
• The will both hit the ground at the same time
• Example Shot a bullet and drop a bullet at the
  same time it would land at the same time.

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Air Resistance

• Air resistance Objects falling through the air
  experience this fluid friction
• Air resistance pushes the object up as it falls
  causing it to slow down

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Air Resistance and Mass

• Air resistance is not the same for all objects
• -A feather will fall slower then a rock because
  of air resistance
• Air resistance increase as the velocity of the
  object increases.
• Eventually air resistance will equal the force of
  gravity and an object could stop falling

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Weight

• Weight is the force of gravity on a person or
  object at the surface of a planet
• Weight mass X acceleration due to gravity
• Weight mass x 9.8m/s²

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Do the Math - weight

• What is the weight of a person with a mass of
  75kg
• Weight mass x acceleration due to gravity
• Weight 75kg x 9.8 m/s²
• Weight 735N

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Law of Universal Gravition

• The law of universal gravitation states that the
  force of gravity acts between all objects in the
  universe
• Any two objects in the universe without exception
  attract each other
• We cannot tell most of the time because the force
  is small