Dynamics the branch of mechanics concerned
with the motion of bodies under the action of forces.The Newtons’s laws of the
motion are the action of dynamics.These laws provide an example of the width of
principals under nature functions.The Newton’s laws were monumental work that
has made him the person who he was.This transition was characterized by a
revolutionary change in the way people thought about physical universe.
Newton started to explain phenomena through the
universe. What lay within was to apply everywhere, and to every process. The
trajectory taken by a cannon ball was to be governed by the same laws which
governed the orbits of the other planets. As the start of his work, he states
his definitions of mass, momentum, inertia and forces, both through contact and
at a fixed distance. He states his three laws:
First Law Everybody in it’s state of the rest, or of uniform motion in a right
line,it be completed to change that state by forces impressed in it thereon.
Second Law The alteration of motion is to the motive force impressed; and is made
in the direction of the right line in which that force is impressed.
Third Law Every action there is always opposed an equal reaction: or the mutual
actions of two bodies upon each other are always equal, and directed to
It is broadly divided into
three books, each of this books which alone would eclipse almost any other.
Books One and Two are titled Of the Motion of Bodies, being split into two analyses.
The third book of Isaac Newton is titled The System of the World.
1-The first book organised
and systematised principles, some of which were at least dimly understood
before, but these principles had never been organised together into a system of
analysis for application .
2-The second book sets out
to explain motion on Earth, where motion does not occur in: the details of
motion in resisting media. It is here that Newton departs from his program of
deducing physical behaviour based on his laws: he finds but little use for them
3- The third book set
forth his solutions to problems in celestial dynamics, with great success.
Kepler’s Laws of Planetary Motion had resulted from Newton’s own, and he
performed exhaustive analyses of the Solar System.
Galileo Galilei (1564–1642), these descriptions of motion: he
was the first of the modern dynamicists. He was in the workings of both the Parisian and Mertonian
schools. From these, he started into the still poorly understood field of
kinetics. To move forward, he was successful of the ancient sciences:
Archimedes’ hydrostatics. He took those principles as inspiration to examine
the motion of a falling object. He utilised no mixed–body theory of matter.
Instead, he treated the bodies, and the media through which they traveled, in
terms of their densities . Archimedes’ propositions explain the forces of
buoyancy in equilibrium: they detail where an object will rest in a body of
water. Galileo extended these principles from static into dynamic concepts.
Archimedes explained the behaviour of bodies and
their natural positions of rest. Galileo took this notion and applied it to
bodies in motion. His monumental postulation was that buoyancy, in addition to
determining a body’s position of rest, furthermore determines how fast a body
will reach that position of rest. He used this force of buoyancy to try to
explain why objects fell at the speed they did. It is wrong to say that he
devised a dynamical law based on static principles. His theorems are a
generalisation of Archimedes’ static principles, which are then derivable from
Galileo’s: the converse is untrue. These notions were not new. Instead of using
a ratio of weight to resistance in order to explain motion, Galileo described
it as a natural motion from which was subtracted the effect of the medium.
Instead of having velocity determined by the ratio of a body’s weight to the
medium’s resistance, it was to be determined by a natural value minus some part
due to the resistance of the medium. The approach, ingenious though it was, led
to no hoped for grand principle. The comparison between Galileo and Avempace is
commonly drawn, as Avempace had postulated the same kind of thing: discarding
the Aristotelian ratio. Galileo was certainly aware of Avempace’s work, through
what Averr¨oes wrote of it. It is unfair to say that Avempace was the
originator of this sort of analysis, as it predates him by hundreds of years.
This theory again goes
back to John Philoponus, who was also well known to Galileo. Additionally,
Avempace did not postulate Galileo’s explanations for the causes of motion.