Here are some circle formulas that might be useful to you
How will we use these formulas?
^{
Radius = 2
Use
this for the
earth with a
radius of one
earth radius
Radius = 1
Radius = .5
Circumference of the Circle
2
r
2 * 3.14 * 2
=
12.56
2 * 3.14 * 1
= 6.28
2 * 3.14 *
.5
=
3.14
Area of a Circle
3.14 * (2 * 2)
=
12.56
3.14 * (1 * 1)
=
3.14
3.14 * (.5 * .5)
=
0.785
Surface of a Sphere
4 * 3.14 * (2 * 2)
=
50.48
4 * 3.14 *
(1 * 1 )
=
12.56
4 * 3.14 *
(.5 * .5
)
=
3.14
Volume of a Sphere
(the inside)
4 * 3.14 * (2 * 2 * 2)
3
=
33.49
4 * 3.14 * (1 * 1
*1)
3
= 4.18
4 * 3.14 *
(.5*
.5 .5)
3
=
0.52
NOTE:
Using these numbers
the volume of the
earth = 4.18
When you work out the numbers for your own planet,
you can use these formulas.
If you let the radius of the earth = 1 you can compare
the sizes of the planets with each other without getting entangled
in enormous numbers.
Using the radius of the earth = 1, a larger planet
might have a radius of, perhaps, 1.3.
A smaller planet might have a radius of, perhaps,
0.75.
Check the page on Statistics on Planets
and Moons to get some ideas of possible sizes.
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© 1998, 2003. Elizabeth Anne
Viau. All rights reserved. This material may be used by
individuals for instructional purposes but not sold. Please inform
the author if you use it at
eviau@earthlink.net.
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