# Rearranging an equation for pressure

1. Sep 15, 2004

### Katpea

I'm having big problems rearranging the following equation which calculates the pressure at the centre of Earth, to find R:

P = 2(pi*G/3)*ρ2 R2

Logically to me it would be:

R = 2(pi*G/3P)*ρ2 square rooted (but i'm pretty certain this isn't right!)

I've spent ages trying to sort it out and have resorted to randomly placing the figures in an attempt to find R (radius of the earth which is known already)!!

If anyone could help me sort it out in my head so that I can then rearrange the equation it would be much appreciated!!

2. Sep 15, 2004

### Staff: Mentor

Starting with:
P = 2(pi*G/3)*ρ2 R2
Isolate R2:
R2 = 3P/(2 pi G ρ2)
Now take the square root:
R = 1/ρ sqrt(3P/(2 pi G))

Last edited: Sep 15, 2004
3. Sep 15, 2004

### joyful55

We need batter graphics. I'm having a hard time reading equations while trying to decipher the notations.

4. Sep 15, 2004

### K.J.Healey

What you did was on the left you should have gotten (1/R) not R, because you divided. Thats where you went wrong.