Concepts in Action Chapter 12

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Concepts in ActionChapter 12

• Forces as agents of change
• Forces ONLY push or pullNothing else!!

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The big 4

• There are only 4 forces in the universe
• Mother nature always amazes me with the
  simplicity of designin all the universe only 4
  forces!
• If you can come up with 5 let us knowNobel
  Prize awaits!!
• Actually there might be fewer than 4there might
  in fact only be ONE force!!!

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Einstein

• Albert Einstein tried to prove that the 4 forces
  WERE just all aspects of one single universal
  force.butwe havent proved that yetsofor
  nowwe recognize 4 forces in the universe.
• 1. Gravity
• 2. Electromagnetism
• 3. Strong
• 4. Weak

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Gravity, says author Wysession

• Gravity is the most important force acting over
  long distances and is responsible for large scale
  motions in spaceplanets revolving around the
  sunyou dropping your pencil to the floor.
• Interestingly, it is also the weakest of the 4
  forces AND it only has an attractive (pulling)
  nature.
• What makes it so important is that is is a
  measurable interaction between EVERY two masses.
• Because it decays at a moderate rate as distances
  between masses increases, it is truly the most
  dominant force between macroscopic objects over
  measurably significant distances.

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Strong and Weak forces

• Both of these forces are much stronger in their
  effects than the force of gravity
• BUT
• These forces act over very SHORT distances. These
  forces decay RAPIDLY as the distances increase.
• AND.
• These forces act at the subatomic level. They are
  not measurable at macroscopic distances.
• The strong force holds the nucleus of an atom
  togetherrecall that protons do not want to be
  too close thus the strong force acts to HOLD a
  nucleus together.
• The weak forceweak relative only to the strong
  force
• Is responsible for radioactive decay of large
  nuclei.
• This course is not interested in either of these
  forces so this is all you need to know at this
  point. More later.

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The electromagnetic force

• This is also very important to your daily life.
• You do not fall apart because of the electric
  forces, the positive and negative charges that
  keep atoms bonded to other atoms.
• The E-M force is obviously the force of
  electricity and the forces involves with magnetic
  behaviors.
• It is the E-M force that prevents you from ever
  touching anythingelectrons repel!
• It is E-M forces that produce friction!!

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FMA

• Arguably this is the most important equation in
  all of science.
• It is Newtons Second Law of Motion.
• It describes the interaction between forces as
  cause and changes in behavior as the effect.
• F is a force, any push or pull
• M is the mass. Condensed energy that is made of
  atoms, takes up space, has weight.
• A is any change in the speed or direction of an
  object caused by a force.

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More about Einstein

• Matter and energy are really two variations of
  the same thingtwo sides of the same coin
• Mater might be thought of as condensed energy
• Energy is the ability to do work
• Einstein taught us that fact when he wrote
• EMCC

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Furthermore

• Einstein realized that gravity distorted space
• Gravity, he thought, was caused because matter
  distorted space
• The way rolling a bowling ball across a sheet
  would make indentations and anything rolled
  across the sheet will roll into that indentation
  just like letting go of a pencil will cause it to
  drop into the hole created by the Earths mass.
• Gravity pullsit pulls even lightso light
  emitted by faraway galaxies is actually bent by
  other galaxies as it travels across space to our
  eyes
• Thus
• Everything we see is distorted much the same way
  the location of a coin is distorted as you view
  it in the bottom of a pool.

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Vectors

• Force is a vector.
• A vector is a measurement that has both a
  quantity AND a direction that matters!
• The SI unit of forces is always the NEWTON, N.
• It doesnt matter what kind of forceALL forces
  are measured in SI units, N.
• In the USA we use pounds (lbs) to measure forces.

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Total forces

• If all the forces are added, making sure to be
  careful of directions, and the net force is ZERO
  then there will be ZERO acceleration. That means
  that the object will not accelerate which means
  that the object will not change its behavior
  which means the object will continue to do
  whatever it was, is, doing.

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Net Forces

• An object will ONLY change its behavior IF and
  WHEN there is some unbalanced force acting on the
  object.
• Then and only then will and object accelerate
  so..
• It is understood that FMA
• Means that the F means NET FORCE even though
  it is not written outall scientists understand
  it to mean net forcethat is the amount of
  unblanced force that is acting.

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Friction

• Friction is a force.
• It is a vector.
• It only pushes.
• It always acts opposite to the direction of
  intended or actual motion.
• It is E-M in nature.
• It has to do with the roughness or smoothness of
  the two surfaces in question.
• Friction can be static, sliding or fluid.
• What holds this room together??? Friction and air
  pressure. Thats it. Just friction and air
  pressure!!

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Newtons three laws!!!

• Isaac Newtonwithout contradiction one of the
  smartest humans ever to have lived on this
  planet.
• He explained HOW and WHY ALL objects move!
• In his first law, Newton realized that all matter
  had a property called INERTIA.
• Inertia simply means that objects do not want to
  change their behavior.
• In his second law, Newton explained that to
  change the behavior of an object a force is
  required.
• In his third law he told us that for every action
  there will be an equal but oppositely directed
  reaction.