# Making r the subject

• September 27th 2009, 08:10 PM
Donut
Making r the subject
Hey guys,

As Im a noob at maths I need your help in making r the subject so I can figure out the radius of my nanoparticles. Can someone please help :)

http://a.imagehost.org/t/0280/Effective_mass.jpg
• September 27th 2009, 08:34 PM
pickslides
Hi Donut

Mulitply both sides through by $r^2$

you can then use the quadratic formula to solve for r.
• September 27th 2009, 09:14 PM
Donut
hmm thats what I thought I should do but I get keep getting this obscenely small number. Back to the drawing board I guess >_<

Thanks for the reply

I might post up all my previous working in a sec and see if someone can see the holes in it.
• September 27th 2009, 09:31 PM
Donut
• September 27th 2009, 11:06 PM
Donut
If I can find out that all the above maths is correct it would be a massive help (Nod)
• September 28th 2009, 02:29 PM
pickslides
Take your solutions for r and sub them into the RHS of the equation. Does it give you the LHS?