| Simple Geometry |
| Circle, circumference |
2 * [pi] * r |
| Circle, area |
[pi] * r2 |
| Sphere, volume |
(4/3) * [pi] * r3 |
| Sphere, area |
4 * [pi] * r2 |
Newton's law of gravity |
| Useful for calculating the gravitational force (F) on the surface of a planet. (F) is in m/s2 |
F = G * (m / r2)
m = objects mass in kilograms [kg]
r = objects radius in meters [m]
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Calculating escape velocity |
| Calculate escape velocity vesc. vesc is in m/s |
vesc = (2 * G * (m / r))1/2
m = objects mass in kilograms [kg]
r = objects radius in meters [m]
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Calculating orbital period |
| Calculate orbital period for a planet around a star. It's so simple, it's scary! :) |
P = R3/2
P = Orbital period in years (Earth years)
R = Distance between host star and planet in astronomical units (AU)
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Hubble's law |
Used to calculate the expansion of the Universe.
The speed (v) at which a galaxy seems to move away from us is proportional to the distance (r) to that galaxy. |
v = H * r
v = velocity (speed)
H = Hubble's constant (about 71km/s/Mpc) (Mpc=Mega parsec)
r = Distance
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Density |
| Density is of course mass/volume. Density (D) is usually in metric tons / m3. |
D=m/V
m = objects mass in metric tons [t], (1t=1000kg)
V = objects volume in meters3 [m3]
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