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Near Earth's surface, the acceleration due to gravity, accurate to 2 significant figures, is 9.8 m/s 2 (32 ft/s 2). This means that, ignoring the effects of air resistance , the speed of an object falling freely will increase by about 9.8 metres per second (32 ft/s) every second.
The Schiehallion experiment, proposed in 1772 and completed in 1776, was the first successful measurement of the mean density of the Earth, and thus indirectly of the gravitational constant. The result reported by Charles Hutton (1778) suggested a density of 4.5 g/cm 3 (4 + 1 / 2 times the density of water), about 20% below the modern ...
From this it follows that the average density of Earth is approximately 1.8 times the density of the mountain. [15] [18] [19] Hutton took a density of 2,500 kg·m −3 for Schiehallion, and announced that the density of the Earth was 1.8 times this, or 4,500 kg·m −3, [18] less than 20% away from the modern value of 5,515 kg·m −3. [20]
Earth's density varies considerably, between less than 2700 kg/m 3 in the upper crust to as much as 13 000 kg/m 3 in the inner core. [13] The Earth's core accounts for 15% of Earth's volume but more than 30% of the mass, the mantle for 84% of the volume and close to 70% of the mass, while the crust accounts for less than 1% of the mass. [13]
For example, at a radius of 6600 km (about 200 km above Earth's surface) J 3 /(J 2 r) is about 0.002; i.e., the correction to the "J 2 force" from the "J 3 term" is in the order of 2 permille. The negative value of J 3 implies that for a point mass in Earth's equatorial plane the gravitational force is tilted slightly towards the south due to ...
The type of gravity model used for the Earth depends upon the degree of fidelity required for a given problem. For many problems such as aircraft simulation, it may be sufficient to consider gravity to be a constant, defined as: [2] = = 9.80665 m/s 2 (32.1740 ft/s 2)
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.
In physics, gravity (from Latin gravitas 'weight' [1]) is a fundamental interaction primarily observed as a 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.