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Encyclopedia > Tidal force
Comet Shoemaker-Levy 9 after breaking up under the influence of Jupiter's tidal forces.
Comet Shoemaker-Levy 9 after breaking up under the influence of Jupiter's tidal forces.

The tidal force is a secondary effect of the force of gravity and is responsible for the tides. It arises because the gravitational field is not constant across a body's diameter. Image File history File links Download high resolution version (1548x600, 234 KB) Summary Comet Shoemaker-Levy after breaking up under the influence of Jupiters tidal forces. ... Image File history File links Download high resolution version (1548x600, 234 KB) Summary Comet Shoemaker-Levy after breaking up under the influence of Jupiters tidal forces. ... Hubble Space Telescope image of Comet Shoemaker-Levy 9, taken on May 17, 1994. ... In physics, the force experienced by a body is defined as the rate of change of momentum with time. ... Gravity is a force of attraction that acts between bodies that have mass. ... It has been suggested that Earth tide be merged into this article or section. ... The gravitational field is a field (physics), generated by massive objects, that determines the magnitude and direction of gravitation experienced by other massive objects. ...

Contents

Explanation

When a body (body 1) is acted on by the gravity of another body (body 2), the field can vary significantly on body 1 between the side of the body facing body 2 and the side facing away from body 2. This causes strains on both bodies and may distort them or even, in extreme cases, break one or the other apart. These strains would not occur if the gravitational field is uniform, since a uniform field only causes the entire body to accelerate together in the same direction and at the same rate. The magnitude of an electric field surrounding two equally charged (repelling) particles. ...

Saturn's rings are inside the orbits of its moons. Tidal forces prevented the material in the rings from coalescing gravitationally to form moons.
Saturn's rings are inside the orbits of its moons. Tidal forces prevented the material in the rings from coalescing gravitationally to form moons.

The figure shows Comet Shoemaker-Levy 9 after it had broken up under the influence of Jupiter's tidal forces. The comet was falling into Jupiter, and the parts of the comet closest to Jupiter fell with a greater acceleration, due to the greater gravitational force. From the point of view of an observer riding on the comet, it would appear that the parts in front split off in the forward direction, while the parts in back split off in the backward direction. In reality, however, all parts of the comet were accelerating toward Jupiter, but at different rates. Image File history File links Saturn-cassini-March-27-2004. ... Image File history File links Saturn-cassini-March-27-2004. ... Note: This article contains special characters. ... Hubble Space Telescope image of Comet Shoemaker-Levy 9, taken on May 17, 1994. ... Adjectives: Jovian Atmosphere Surface pressure: 20–200 kPa[4] (cloud layer) Composition: ~86% H2 ~13% Helium 0. ...


Effects of tidal forces

In the case of an elastic sphere, the effect of a tidal force is to distort the shape of the body without any change in volume. The sphere becomes an ellipsoid, with two bulges, pointing towards and away from the other body. This is essentially what happens to the Earth's oceans. Although the Earth is not falling along a line directly toward the moon, the Earth is continuously accelerating due to the moon's gravitational forces, causing it to wobble around their common center of mass. All parts of the Earth accelerate in response to the moon's gravitational forces, but to an observer on the Earth, it appears that the Earth's center remains at rest, while water in the oceans is redistributed to form bulges on the sides near the moon and far from the moon. 3D rendering of an ellipsoid In mathematics, an ellipsoid is a type of quadric that is a higher dimensional analogue of an ellipse. ... Look up Bulge in Wiktionary, the free dictionary. ... In physics, the center of mass of a system of particles is a specific point at which, for many purposes, the systems mass behaves as if it were concentrated. ...


When a body rotates while subject to tidal forces, internal friction results in the gradual dissipation of its rotational kinetic energy as heat. If the body is close enough to its primary, this can result in a rotation which is tidally locked to the orbital motion, as in the case of the Earth's moon. Tidal heating produces dramatic volcanic effects on Jupiter's moon Io. Atmospheric characteristics Atmospheric pressure trace Sulfur dioxide 90% Io (eye-oe, IPA: , Greek Ῑώ) is the innermost of the four Galilean moons of Jupiter. ...


Mathematical treatment

For a given (externally generated) gravitational field, the tidal acceleration at a point with respect to a body is obtained by vectorially subtracting the gravitational acceleration at the center of the body from the actual gravitational acceleration at the point. Correspondingly, the term tidal force is used to describe the forces due to tidal acceleration. Note that for these purposes the only gravitational field considered is the external one; the gravitational field of the body (as shown in the graphic) is not relevant. In physics and in vector calculus, a spatial vector, or simply vector, is a concept characterized by a magnitude and a direction. ...

Graphic of tidal forces; the gravity field is generated by a body to the right. The top picture shows the gravitational forces; the bottom shows their residual once the field at the centre of the sphere is subtracted; this is the tidal force. See calculated tidal forces for a more exact version
Graphic of tidal forces; the gravity field is generated by a body to the right. The top picture shows the gravitational forces; the bottom shows their residual once the field at the centre of the sphere is subtracted; this is the tidal force. See calculated tidal forces for a more exact version

Tidal acceleration does not require rotation or orbiting bodies; e.g. the body may be freefalling in a straight line under the influence of a gravitational field while still being influenced by (changing) tidal acceleration. Diagram of tidal forces. ... Diagram of tidal forces. ... Tidal forces resulting from Newtonian gravity. ... Freefall or free fall in the strict sense is the condition of acceleration which is due only to gravity. ...


Suppose that the gravitational field is due to one other body: linearizing Newton's law of gravitation around the centre of the reference body yields an approximate inverse cube law. The derivation of the equation of tidal force proceeds as follows: Sir Isaac Newton, (4 January 1643 – 31 March 1727) [ OS: 25 December 1642 – 20 March 1727][1] was an English physicist, mathematician, astronomer, natural philosopher, and alchemist, regarded by many as the greatest figure in the history of science. ... See Also: Watt In physics, a power law relationship between two scalar quantities x and y is any such that the relationship can be written as where a (the constant of proportionality) and k (the exponent of the power law) are constants. ...


The tidal force is the difference between the gravitational forces at 2 different distances:




Find a common denominator





FOIL the (R + Δr)2 's





Factor out GMm





R2 and R2 cancel each other





Eliminate that which is not significant. Take advantage that R >> r





Cancel the R in the numerator with one of the R's in the denominator





Rearrange:





where G is the gravitational constant, M is the mass of the body producing the field, m is the mass on which the tidal force acts, R is the distance between the two bodies and rR is the distance from the reference body's center along the axis. This tidal force acts outwards both at the near side and at the far side of the body, leading to a bulge on both sides. According to the law of universal gravitation, the attractive force between two bodies is proportional to the product of their masses and inversely proportional to the square of the distance between them. ... Unsolved problems in physics: What causes anything to have mass? The U.S. National Prototype Kilogram, which currently serves as the primary standard for measuring mass in the U.S. Mass is the property of a physical object that quantifies the amount of matter and energy it is equivalent to. ...


The tidal forces can also be calculated away from the axis connecting the bodies. In the plane perpendicular to the axis, the tidal force is directed inwards, and its magnitude is Ft / 2 in the linear approximation ( 1). Tidal forces resulting from Newtonian gravity. ...


Tidal effects become particularly pronounced near small bodies of high mass, such as neutron stars or black holes, where they are responsible for the "spaghettification" of infalling matter. Tidal forces, in combination with centripetal forces, create the oceanic tide of Earth's oceans, where the attracting bodies are the Moon and the Sun. A neutron star is one of the few possible endpoints of stellar evolution. ... For other senses of this word, see black hole (disambiguation). ... Click here for animated version Spaghettification is caused by the gravitational forces acting on the four objects. ... The centripetal force is the external force required to make the body move in a circular path with uniform speed and directed towards the center. ... It has been suggested that Earth tide be merged into this article or section. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... Apparent magnitude: up to -12. ... The Sun is the star at the center of the Solar System. ...


Tidal forces are also responsible for tidal locking. Tidal locking makes one side of an astronomical body always face another, like the Moon facing the Earth. ...


See also

In oceanography, tidal resonance is a phenomenon perhaps best exemplified in the Bay of Fundy. ... The Roche limit, sometimes referred to as the Roche radius, is the distance within which a celestial body held together only by its own gravity will disintegrate due to a second celestial bodys tidal forces exceeding the first bodys gravitational self-attraction. ... It has been suggested that Tidal friction be merged into this article or section. ... The Andromeda Galaxy. ...

External links


  Results from FactBites:
 
Tidal force Summary (1058 words)
Tidal forces are responsible for the ocean tides we observe on Earth.
The tidal force is a secondary effect of the force of gravity and is responsible for the tides.
Tidal forces, in combination with centripetal forces, create the oceanic tide of Earth's oceans, where the attracting bodies are the Moon and the Sun.
NOAA, Our Restless Tides, Explanation of Astronomical Factors, Tides and Tidal Currents (2032 words)
The tide-raising forces at the earth's surface thus result from a combination of basic forces: (1) the force of gravitation exerted by the moon (and sun) upon the earth; and (2) centrifugal forces produced by the revolutions of the earth and moon (and earth and sun) around their common center-of-gravity (mass) or barycenter.
While the effect of this centrifugal force is constant for all positions on the earth, the effect of the external gravitational force produced by another astronomical body may be different at different positions on the earth because the magnitude of the gravitational force exerted varies with the distance of the attracting body.
The force is zero at the points on the earth's surface directly beneath and on the opposite side of the earth from the moon (since in these positions, the lunar gravitational force is exerted in the vertical - i.e., opposed to, and in the direction of the earth-gravity, respectively).
  More results at FactBites »

 
 

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