Gravitation
Kepler's Laws
- The orbit of each planet is an ellipse which has the sun at one of its foci.
- Each planet moves in such a way that the line joining it to the sun sweeps out equal areas in equal times.
- The squares of the periods of revolution of the planets about the Sun are proportional to the cubes of their mean distance from it.
Newton's gravitational law
F =
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The gravitational force between two bodies.
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G =
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Universal gravity constant, 6.67 x 10−11 N m2 kg−2
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m1 =
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The mass of the first body.
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m2 =
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The mass of the second body.
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r =
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The distance between the centres of mass of two bodies.
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Black body radiation
temperature of the black body.
- w = 2.90 × 10−3 m K
Stefan's Law
E =
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Rate of energy radiated from the surface of a black body per unit area.
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σ =
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Stefan's constant, 5.67 × 10−8 W m−2 K−4
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T =
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Surface temperature of the black body.
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Stellar Magnitude
Apparent Magnitude
m =
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Apparent magnitude of star.
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I =
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Intensity of light received.
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K =
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a constant
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m1 =
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Apparent magnitude of first star.
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m2 =
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Apparent magnitude of second star.
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I1 =
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Intensity of light received from first star.
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I2 =
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Intensity of light received from second star.
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Absolute Magnitude
m =
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Apparent magnitude of star.
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M =
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Absolute magnitude of star.
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d =
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Distance to star in parsecs.
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