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Old Oct 4th 2018, 01:57 PM   #1
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Join Date: Sep 2018
Posts: 7
Density of Black Hole

So when I tested the sample question I got the right answer. But doing a practice one I feel like I got the wrong answer - it seems way too high:

Black hole mass - 4.31 x 10^6
I calculated Rs to be = 1.27 x 10^7
Average density:
P = m/v

m = (4.31x10^6) x (1.989x10^30)
m = 8.57x10^36 km

v=4/3 x π x r^3
v= 4.3 x π x (4.127x10^7)^3
v= 8.22 x 10^21

P = (8.57x10^26) / (8.22 x 10^21)
P = 1.04 x 10^15 km m^-3

Have I calculated this correctly or have I done something wrong?
When I go on to look a Roche Limit:
1400 kg m^-1 = Sun's average density

r = 2.456(((1.04x10^15)/(1400))^1/3)
r = 2243.17

Which seems way too high?
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