How much do you need to increase the pendulums length by to

[jstretto]

Homework Statement

How much do you need to increase the pendulums length by to double the pendulums period

Homework Equations

T = 2PI sqrt(length/gravity)

The Attempt at a Solution

Answer is 2sqrt(l). But I don't know how to get there. Any help would be greatly appreciated, thanks.

 

[Orodruin]

That answer does not even have the correct physical dimension. Also, please provide your own attempt as per forum rules.

 

[scottdave]

You know the ratio T_new / T_old = 2. Start there.