Uh oh! Wolfram|Alpha doesn't run without JavaScript.
Please enable JavaScript. If you don't know how, you can find instructions
here
.
Once you've done that, refresh this page to start using Wolfram|Alpha.
solve s = 2*pi*r*(r+(v/(pi*r^2))) for r
solve s = 2*pi*r*(r+(v/(pi*r^2))) for r
Natural Language
Math Input
Extended Keyboard