The entire subject of
rigid-body mechanics is formulated on the basis of Newton's three laws of
motion, the validity of which is based on experimental observation. Sir
Issac Newton was the first to state correctly the basic laws governing the
motion of a particle and to demonstrate their validity. They apply to the
motion of particle as measured from non-accelerating reference frame.
First Law. A particle originally at rest, or moving in a
straight line with constant velocity, will remain in this state provided the
particle is not subjected to an unbalanced force.
Second Law. A particle acted upon by an unbalanced force F experiences an acceleration a that has the same direction as the
force and a magnitude that is directly proportional to the force F. If F is applied to particle of mass m, this law may be expressed
mathematically as F = ma
Third Law. The mutual forces of action and reaction between two particles are equal, opposite and collinear.
Third Law. The mutual forces of action and reaction between two particles are equal, opposite and collinear.
Law of Gravitational
Attraction. Shortly after
formulating his three laws of motion, Newton postulated a law governing the
mutual attraction between any two particles. Stated mathematically,
where
F = force of gravitation
between the two particles
G = universal constant of gravitation; according
to experimental evidence, G = 66.73×10-12 N.m2.kg-2
m1, m2
= mass of each of the two particles.
r = distance between the two particles.
r = distance between the two particles.
