# Thread: I NEED someone good at astrology for this.

1. I am not very good at astrophysics or anything, so I come to you guys for help.

If a planet were roughly 1 km in diameter, with ten times the gravity of Earth, what would its mass & density be? What would it's density be comparable to, if comparable to anything?

2.

3. Originally Posted by That_Inquisitive_Guy
I am not very good at astrophysics or anything
Yeah.
Astrology?

If a planet were roughly 1 km in diameter, with ten times the gravity of Earth, what would its mass & density be? What would it's density be comparable to, if comparable to anything?

where M is the mass of the object, r is its radius, and G is the gravitational constant.

If we let ρ = m/V denote the mean density of the object, we can also write this as

4. So, what would it's density be?

5. Originally Posted by That_Inquisitive_Guy
So, what would it's density be?
You don't know how to rearrange an equation?

(3g)/(4piGr) = p.

6. Don't mind the duck, he is a bit impatient. As well as daffy.

Just a couple of things. When you say astrology, you really mean astronomy. And this isn't really astronomy, just general physics. Anyway, in case you need help going the rest of the way...

g for Earth is 9.8 m/s2 so we can approximate g for your planet as 100

r = 1000 m

G = 6.7 * 10-11

pi = 3.14

Now we are ready to go.

From the first equation
mass = g r2 / G = 100 * 10000^2 / 6.7 * 10-11 = 1.5 * 1020 kg

That is about 1/40000 the mass of the Earth.

The volume of the planet is 4/3 pi * r3 = 4.2 * 109 m3

So the density (M/V) = 1.5 * 1020 / 4.2 * 109 kg/m3 = 3.6 * 1010 kg/m3

That is about 10 times denser than a white dwarf and about 10 million times less dense than a neutron star.
http://en.wikipedia.org/wiki/Orders_..._%28density%29

7. astrology = 5% astronomy + 95% B*****t

8. I think you underestimated the bullshit content

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