Acceleration due to gravity: Difference between revisions
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In the [[science]]s, the term '''acceleration due to gravity''' | In the [[science]]s, the term '''acceleration due to gravity''' refers to the value of 9.80656 m/s<sup>2</sup> and is denoted as ''g<sub>n</sub>''. That value was agreed upon by the 3rd General Conference on Weights and Measures (Conférence Générale des Poids et Mesures, CGPM) in 1901.<ref>[http://physics.nist.gov/Document/sp330.pdf The International System of Units (SI), NIST Special Publication 330, 2001 Edition] (pdf page 29 of 77 pdf pages) </ref><ref>[http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf#page=51 Bureau International des Poids et Mesures] (pdf page 51 of 88 pdf pages)</ref> It is also often referred to as the ''local gravitational acceleration'' or the ''standard gravity''. | ||
Any object near the [[earth]] is subject to a [[force]] in the downward direction that causes an [[acceleration]] of magnitude ''g<sub>n</sub>'' toward the surface of the earth. This value serves as an excellent approximation for the local acceleration due to gravity at the surface of the earth, although it is not exact and the actual acceleration varies slightly between different locations around the world. | Any object near the [[earth]] is subject to a [[force]] in the downward direction that causes an [[acceleration]] of magnitude ''g<sub>n</sub>'' toward the surface of the earth. This value serves as an excellent approximation for the local acceleration due to gravity at the surface of the earth, although it is not exact and the actual acceleration varies slightly between different locations around the world. | ||
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:<math>g = G \frac{M}{r^2} </math> | :<math>g = G \frac{M}{r^2} </math> | ||
The magnitude of the acceleration is in [[SI]] units of [[meter]]s per [[second]] squared. | The magnitude of the acceleration is in [[SI]] units of [[meter]]s per [[second]] squared. | ||
Here ''G'' is the [[universal gravitational constant]], ''G'' = 6.67428×10<sup>−11</sup> Nm<sup>2</sup>/kg<sup>2</sup>,<ref> Source: [http://physics.nist.gov/cgi-bin/cuu/Value?bg|search_for=Gravitational CODATA 2006, retrieved 2/24/08 from NIST website]</ref> <math>r</math> is the distance | Here ''G'' is the [[universal gravitational constant]], ''G'' = 6.67428×10<sup>−11</sup> Nm<sup>2</sup>/kg<sup>2</sup>,<ref> Source: [http://physics.nist.gov/cgi-bin/cuu/Value?bg|search_for=Gravitational CODATA 2006, retrieved 2/24/08 from NIST website]</ref> <math>r</math> is the distance from the test object to the centre of mass of the Earth and ''M'' is the mass of the Earth. | ||
In physics, [[acceleration]] is a vector, with an absolute value (magnitude, length) ''g'' and a direction from the center of mass of Earth toward the test object, hence as a vector the acceleration is: | |||
:<math> | :<math> | ||
\vec{g} = - G \frac{M}{r^2} \vec{e}_r \quad \hbox{with}\quad \vec{e}_r \equiv \frac{\vec{r}}{r}. | \vec{g} = - G \frac{M}{r^2} \vec{e}_r \quad \hbox{with}\quad \vec{e}_r \equiv \frac{\vec{r}}{r}. | ||
Revision as of 03:58, 26 February 2008
In the sciences, the term acceleration due to gravity refers to the value of 9.80656 m/s2 and is denoted as gn. That value was agreed upon by the 3rd General Conference on Weights and Measures (Conférence Générale des Poids et Mesures, CGPM) in 1901.[1][2] It is also often referred to as the local gravitational acceleration or the standard gravity.
Any object near the earth is subject to a force in the downward direction that causes an acceleration of magnitude gn toward the surface of the earth. This value serves as an excellent approximation for the local acceleration due to gravity at the surface of the earth, although it is not exact and the actual acceleration varies slightly between different locations around the world.
More generally the acceleration due to gravity refers to the magnitude of the force on some test object due to the mass of another object. Under Newtonian gravity the gravitational field strength, due to a spherically symmetric object of mass M is given by:
The magnitude of the acceleration is in SI units of meters per second squared. Here G is the universal gravitational constant, G = 6.67428×10−11 Nm2/kg2,[3] is the distance from the test object to the centre of mass of the Earth and M is the mass of the Earth.
In physics, acceleration is a vector, with an absolute value (magnitude, length) g and a direction from the center of mass of Earth toward the test object, hence as a vector the acceleration is:
Reference
- ↑ The International System of Units (SI), NIST Special Publication 330, 2001 Edition (pdf page 29 of 77 pdf pages)
- ↑ Bureau International des Poids et Mesures (pdf page 51 of 88 pdf pages)
- ↑ Source: CODATA 2006, retrieved 2/24/08 from NIST website