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Easy math question... Calculating radius of a sphere

force = mass x grav

mass = force / grav

==================

density = mass / volume

volume = mass / density

==================

volume (sphere) = (4/3) x pi x r^3 (i think)

r = [3 x volume (sphere) / (4 x pi)]^1/3

================== combining them gets you

r = [3 x ((force / grav) / density) / (4 x pi)]^1/3

where:
force = weight (given)
grav is a constant
density (given)
pi = 3.14
 
Originally posted by: Wyck
Because I forget how to divide/multiple to get r on the left. Look, math really isnt' my thing.
Click to expand...
Subtract density from both sides. Divide both sides by 4pi. Multiply both sides by 3. Take the cube root of both sides.

 
Originally posted by: Wyck
Hmm, I have here that

weight = density + 4 * pi * radius^3 / 3
Click to expand...

that doesn't make sense because rearranging...

weight - density != 4 * pi * radius^3 / 3 = Volume of a sphere
 
I don't need to do the cube root of everything, radius^3 will be enough. So is this right?

radius^3 = weight - density - 4 / pi * 3

How would I group the numbers on the left?

radius^3 = (weight - density - 4) / pi * 3?
 
Wyck, that doesn't look right.

If you're allowed to leave it in the form of r^3, I got:

Volume = (W/g*D)
R^3 = (3*volume) / (4*pi) = (3 * (W/(g*D)) ) / (4 * pi)

where W = weight, g = gravity (9.8 m/s/s on Earth), D = density.
 
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