Physics for idiots by an idiot, Newtonian mechanics

    The media today is full of documentaries on the wonderful world of physics, the universe, quantum mechanics and a lot of physics subjects.
     The problem is that all of them teach nothing worth of value. The documentaries are there just to make you "WOW!", "OMFG!", "AYYY LMAO".
     To get into the wonderful world of physics you have to start with the basics, which is Newtonian mechanics. Newtonian mechanics is that wonderful subject that you study in your first year at university, it's simple but the professors stress that you should learn it like it's the word of God and they flunk a hell lot of students for not learning it.
     For good reason they flunk legions of students. In learning Newtonian mechanics you learn the principles on which every other subject of physics is built upon.
     Newtonian mechanics is composed of 3 parts:

1. Cinematics - how objects move
2. Dynamics   - why objects move
3. Statics       - why objects don't move, are at equilibrium

      So let's begin with dynamics. Dynamics is concerned with the reason why objects move or grind to a halt.
      If you ever took a moment to reflect about the physical world you would have come to these conclusions:

1. Objects are in 2 states:

• physical objects (cars, people, etc) are stationary

• physical objects move with constant speed or increasing/decreasing speed

   2.  The most important 3 properties of the physical world you can perceive are:

• time
• distance
• mass

Examples:
   "A physical object with a certain mass moved some distance in a period of time. If we split the  distance that the object moved in equal consecutive lengths, the object moved through those equal consecutive lengths in equal amounts of time or in different amounts of time  for each equal and consecutive length."



    The example above gives you an intuitive feeling of what speed and acceleration is:

1.  speed is distance that an object moved in an amount of time : Speed = distance / time.
2.  acceleration  is the variation of speed in time, meaning that the speed of an object increased or decreased with time: Acceleration = (Speed at time t1 - Speed at time t2)/ time.

    The reason why objects start moving with constant speed or variating speed is force. If an object is moving at constant speed that means that initially the object was stationary and a force acted on it for a distance and the start moving. The reason why an object is moving with increasing speed or decreasing speed is that a force is still apllied on it.

    Let's recapitulate: physical objects move and the reason why they move is that a force acted or is applied to them.

    Let's say you find a spring around the house, you play with it and you come to the conclusion that the spring generates a force when compressed. You fix it to a vertical wall and take 3 objects of same size and shape but different masses. You make a little experiment where you compress the spring with those 3 objects and you observe how the objects start moving:
    1. You measure the acceleration that the objects achieve when the spring acts on them,
    2. You measure the acceleration that the objects have after losing contact with the spring.

    At point 1 you measure that the objects have a non zero acceleration, at point 2 you observe that objects have zero (0) acceleration but a constant speed.
    Fooling around with the measured accelerations on a piece of a paper you observe that the acceleration of object 1 times the mass of object 1 is equal to the acceleration of object 2 times the mass of object two equals the mass of object 3 times the acceleration of object 3:

 m1*a1=m2*a2=m3*a3

Congratulations you have found the formula that describes the quantity of force:

FORCE = MASS * ACCELERATION

F= M * A;

  

  Isaac Newton understood this and he put all of the above obersvations into three simple laws, "Newton law's of motion":

1. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

2.  The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector.

3. For every action there is an equal and opposite reaction. Example:  You are on a boat near the shore. You take a paddle and you push against the shore. What you are doing is applying a force on the shore, a force for example F = 20 Newtons. The object you apply force against is the planet earth itself, the earth won't move because its mass is huge and if you calculate earths acceleration for the force you applied using a=F/earth's mass you will see that the acceleration is really really small 0,0.......................01. Earth than applies the same force on you and the boat , you start moving in the opposite direction. The forces that you apply and the reaction  force of earth are equal, they don't cancel each other out because the force you apply has it's application point on the earth(shore) and the reaction ( the force earth is applying back) has its application point on you.