Question

If you double the period of a pendulum, what happens to its length

Answer 1

T = 2π * √(l / g)

2T = 2 (2π * √(l / g)

Here 2π is constant and g is also a constant. So only l can be changed.

So 2 (2π * √(l / g) = 2 (2π * √(lₐ / g)

2 √l = √lₐ

On squaring both sides; lₐ = 4l