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A common misconception occurs between centre of mass and centre of gravity.They are defined in similar ways but are not exactly the same quantity. Centre of mass is the mathematical description of placing all the mass in the region considered to one position, centre of gravity is a real physical quantity, the point of a body where the gravitational force acts.
[1] [2] [3] This is a general physical law derived from empirical observations by what Isaac Newton called inductive reasoning. [4] It is a part of classical mechanics and was formulated in Newton's work Philosophiæ Naturalis Principia Mathematica ("the Principia"), first published on 5 July 1687. The equation for universal gravitation thus ...
For example, the equation above gives the acceleration at 9.820 m/s 2, when GM = 3.986 × 10 14 m 3 /s 2, and R = 6.371 × 10 6 m. The centripetal radius is r = R cos( φ ) , and the centripetal time unit is approximately ( day / 2 π ), reduces this, for r = 5 × 10 6 metres, to 9.79379 m/s 2 , which is closer to the observed value.
In physics, gravity (from Latin gravitas 'weight' [1]) is a fundamental interaction primarily observed as mutual attraction between all things that have mass.Gravity is, by far, the weakest of the four fundamental interactions, approximately 10 38 times weaker than the strong interaction, 10 36 times weaker than the electromagnetic force and 10 29 times weaker than the weak interaction.
At a fixed point on the surface, the magnitude of Earth's gravity results from combined effect of gravitation and the centrifugal force from Earth's rotation. [2] [3] At different points on Earth's surface, the free fall acceleration ranges from 9.764 to 9.834 m/s 2 (32.03 to 32.26 ft/s 2), [4] depending on altitude, latitude, and longitude.
The first equation shows that, after one second, an object will have fallen a distance of 1/2 × 9.8 × 1 2 = 4.9 m. After two seconds it will have fallen 1/2 × 9.8 × 2 2 = 19.6 m; and so on. On the other hand, the penultimate equation becomes grossly inaccurate at great distances.
Gravity on the Earth's surface varies by around 0.7%, from 9.7639 m/s 2 on the Nevado Huascarán mountain in Peru to 9.8337 m/s 2 at the surface of the Arctic Ocean. [6] In large cities, it ranges from 9.7806 m/s 2 [7] in Kuala Lumpur, Mexico City, and Singapore to 9.825 m/s 2 in Oslo and Helsinki.
For two pairwise interacting point particles, the gravitational potential energy is the work that an outside agent must do in order to quasi-statically bring the masses together (which is therefore, exactly opposite the work done by the gravitational field on the masses): = = where is the displacement vector of the mass, is gravitational force acting on it and denotes scalar product.