DOI:
VOLUME 2 – APRIL ISSUE 2
Luigi Antonio Pezone*
ABSTRACT
The first to study the principle of inertia was Galileo (1564 -1642), who stated that a body will continue to move in uniform rectilinear motion, or will remain still, if it is not subject to external forces. Even today, many who teach the principle of inertia fail to say that Galileo was referring to the movement of bodies in the empty space of the universe, where there is no friction with the atmospheric air surrounding the Earth. The same gravitational force would deviate space bodies toward the Earth as it deviates the air molecules that form the Earth's atmosphere. In fact, Galileo was the first to discover the gravitational force and its value of 9.81 m/s2, which condenses atmospheric air to the pressure of one atmosphere. Therefore, he could not forget the resistance to motion of atmospheric air. The value of atmospheric pressure was measured for the first time with a special invention by his disciple, Evangelista Torricelli (1608 - 1647), who with a glass tube and a basin filled with mercury demonstrated that atmospheric pressure raised the mercury in the glass tube by 760 mm. Later, he also formulated Torricelli's law which states that the speed of a fluid exiting from a hole (with a very small section compared to the dimensions of the container) is equal to the square root of the double product of the acceleration of gravity and the distance "h" between the free surface of the fluid and the center of the hole that has been made. This demonstrates that the value of the acceleration of terrestrial gravity of 9.81 m/s2 was already known when Newton (1642 - 1726) legislated that a mass of one kilogram, in proximity to the earth's surface, undergoes an acceleration of approximately 9.81 m/s2. In fact, 1 kgpeso= 9,81 N in honor of Newton. So, Galileo and Newton are respectively the discoverer and the legislature of the gravitational force, while Torricelli is the inventor and experimenter.
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