Newtonian Mechanics

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Newtonian Mechanics
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• Corpus omne persevare in status suo quiescendi
  vel movendi uniformiter in directum nisi
  quantenus illud a viribus impressis cogitur
  statum suum mutare.

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Newtons First Law

• Every body continues in its state of rest or
  uniform motion in a straight line unless
  compelled by an external force to change that
  state.

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Galileo and the Law of Inertia

• Galileo looked at motion differently.
• If you push an object across a surface, the
  smoothness or lubrication on the surface affects
  how hard you have to push the object to keep the
  object moving.
• As the surface gets slicker and slicker, the
  force required gets smaller. Eventually, the
  force required to keep the object moving would
  decrease to zero. This leads to

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The Law of Inertia

• The Law of Inertia states that a body once set in
  motion and thereafter undisturbed will continue
  in uniform motion forever, all by itself.
• This can be simplified to, An object continues
  doing what it is already doing.

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Newton add to the Law of Inertia

• Newton used Galileos Law of Inertia as the basis
  for his first law that was published in his 1687
  work, Principia Mathematical Principles of
  Natural Philosphy.
• Newton extended this law with other laws of
  motion.

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Newtons Life

• Born December 25, 1642
• Gregorian calendar January 4, 1643 but it was
  not adopted until 1752.
• Started Trinity College June 1661 and wanted to
  be a lawyer.
• The plague closed Cambridge for two years
  starting in 1665. Newton did work at home.
• Appointed to the Lucasian Chair in 1669.

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More on Newton

• 1687 published Philosophiae Naturalis Principia
  Mathematica
• 1693 had a nervous breakdown
• 1696 appointed Warden of the Royal Mint
• 1699 appointed Master of the Royal Mint
• 1703 elected president of the Royal Society
• 1708 Knighted
• 1727 died

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Inertia and Mass

• So strong is our belief in the Law of Inertia, we
  try to use inertia reference frames.
• Inertial reference frames are frames of
  reference where the Law of Inertia does work.
• The rotating frame of reference is an example of
  a not inertial reference frame. Our minds start
  to create forces to explain apparent deviations
  from the expected motions.

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A Word About Forces

• Forces are defined as a push or pull on an
  object.
• Forces are vector quantities.
• In the Metric System of measurement, forces are
  measured in Newtons (N).
• 1 N 1 kgm/s²

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The Fundamental Forces

• There are four fundamental forces in Nature. All
  other forces are really combinations of the four
  fundamental forces.
• The four fundamental forces are
• Gravity
• Electric-Magnetic Force
• Strong Nuclear Force
• Weak Nuclear Force

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Force of Gravity

• The force of attraction between any two masses.
• This force is proportional to the product of the
  masses and is inversely proportional to the
  square of the distance between the masses.

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Electric Force

• The electric and the magnetic force are two
  different aspects of the same force.
• The electric force can be an attractive or a
  repulsive force and depends on the charges
  involved and the distance between the charges.

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Strong Nuclear Force

• The strong nuclear force is the attractive force
  between two nucleons (neutrons or protons).
• The strong nuclear force is responsible for
  holding the nucleus of an atom together.

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Weak Nuclear Force

• The weak nuclear force is a repulsive force that
  is responsible for radioactivity.

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Common Forces

• Normal Force
• The force a surface exerts on an object.
• The normal force is perpendicular to the
  surface.
• Tension
• The force that is exerted by a rope, string,
  cable etc. on an object.
• Remember, you cant push with a rope.
• Elastic Force
• The force exerted by stretching or compressing
  an elastic object.

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More Common Forces

• Friction
• The force between two surfaces acting parallel
  to the surface.
• Buoyancy
• The force a fluid applies to an object due to
  differences in density.

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Units of Force

• In the SI system, forces are measured in Newtons
  (N).
• A Newton is equivalent to a kilogrammetre/second
  ².
• 1 N 1 kgm/s²

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