Laws of Motion

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Laws of Motion

• Mrs. Calhoun

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Newtons Laws

• Sir Isaac Newtons laws describe motion and the
  forces that act upon it.

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Newtons First Law

• An object at rest will remain at rest and an
  object in motion will remain in motion unless a
  force acts upon it.
• It predicts the behavior of objects for which all
  existing forces are balanced. The first law -
  sometimes referred to as the "law of inertia"
• The net force is zero. The objects are moving or
  standing still unless the force acts on them.

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(No Transcript)
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• If something pushes or pulls on an object, we say
  that a force is acting on the object. 
• A force is a vector.  It has magnitude and
  direction.  Vectors are usually shown as arrows.
• If two or more forces act on an object, then the
  net force acting on the object is the vector sum
  of all the forces.

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Forces
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Inertia

• Objects tend to maintain their state of motion,
  called inertia. Inertia is the tendency of an
  object to resist being moved or, if moving, to
  continue moving at a constant velocity.
• It is harder to push a car than it is to push
  your book across the table because the car has
  more.
• INERTIA!
• Why?
• It takes more force to start the car moving, and
  more to stop the car than it does to start moving
  a book.

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Newtons Second Law

• Describes the relationship between mass, force,
  and acceleration
• The force acting on an object equals the objects
  mass times its acceleration.
• Fma

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Newton's Laws of Motion
Newtons Second Law The acceleration of a body
is inversely proportional to its mass, directly
proportional to the net force and in the same
direction as the net force.   
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Newton

• Force is measured in a unit called a Newton
• 1N 1kg x 1m/s/s

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Newtons Second Law

• Acceleration force / mass
• AF/m

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Formulas

• Fma Unit for Force N
• aF/m Unit for acceleration m/s/s
• m ?
• m F/a Unit for mass kg, g, lb

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Which law is it?

• blood rushes from your head to your feet while
  quickly stopping when riding on a descending
  elevator.
• to dislodge ketchup from the bottom of a ketchup
  bottle, it is often turned upside down and,
  thrusted downward at high speeds and then
  abruptly halted.
• headrests are placed in cars to prevent whiplash
  injuries during rear-end collisions.

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• FIRST!

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Which law is it?