Saturday, 17 September 2011

Newton and Mechanics

Starting about 1665, at the age of 23, Newton enunciated the principles of mechanics, formulated the law of universal gravitation, separated white light into colors, proposed a theory for the propagation of light, and invented differential and integral calculus. Newton's contributions covered an enormous range of natural phenomena: He was thus able to show that not only Kepler's laws of planetary motion but also Galileo's discoveries of falling bodies follow a combination of his own second law of motion and the law of gravitation, and to predict the appearance of comets, explain the effect of the moon in producing the tides, and explain the precession of the equinoxes. 
The Development of Mechanics 
The subsequent development of physics owes much to Newton's laws of motion , notably the second, which states that the force needed to accelerate an object will be proportional to its mass times the acceleration. If the force and the initial position and velocity of a body are given, subsequent positions and velocities can be computed, although the force may vary with time or position; in the latter case, Newton's calculus must be applied. This simple law contained another important aspect: Each body has an inherent property, its inertial mass, which influences its motion. The greater this mass, the slower the change of velocity when a given force is impressed. Even today, the law retains its practical utility, as long as the body is not very small, not very massive, and not moving extremely rapidly. Newton's third law, expressed simply as "for every action there is an equal and opposite reaction," recognizes, in more sophisticated modern terms, that all forces between particles come in oppositely directed pairs, although not necessarily along the line joining the particles

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