A part of
the mechanics in which we study motion and it's causes is called
dynamics. Although all the physicians from Arhimed on have been
trying to understand the causes of motion, only Galileo and Newton
have succeeded. The question of the relation of the force, and motion
is in fact the central question of dynamics. From the experience
we know that when we move the object we must perform force on it
all the time. It seems that it is the constant work of the force
that is needed to obtain the constant speed. That was the belief
that prevailed at the antique physicians. From this belief that
without this force work bodies stay in the standstill position.
Of course, this hypothesis could not explain the motion of the heavenly
bodies. Two thousand years later Galileo concluded that everybody
will keeps it's speed, until it appears a cause of acceleration
or deceleration. This conclusion is in fact the Law of inertia.
axioms - the basic laws of motion
to Newton the force is: a cause of the change in the motion of the
body along any quantity or direction. Each force has it's point
of application, a point in which it acts, the direction of acting
and the quantity. Force is in fact a vector. The forces can be recognized
only according to the direction of it's action. According to Newton
mass is the resistance (inertia) that body
uses to resist to the change in motion. In this moment it is
useful to emphasize the difference between the mass and the weight.
The weight is the force by which some body presses the surface (expressed
in newtons - N) and mass is the ratio of force and acceleration
(expressed in kilograms - kg).
First Newton's law - the law of inertia
body stays in a stand still position or uniform motion along the
straight line up to the moment when it under the work of some outer
forces changes the direction of the motion (law on inertia).
Second Newton's law - the law of force
in motion is proportional to the force that works in the direction
of the straight line in which works the force -s=1/2gt2
Third Newton's law - the law of action and reaction
work has always got the opposite and equal contra work, or to say
the work of the two bodies one to another are always equal and of
opposite direction - m1a1=m2a2
work and energy
the concept of work is strictly defined and is related to resisting
the force on the given path - work=force x passed path.