Answer:
L = ¼ k g / m
Explanation:
This is an interesting exercise, in the first case the spring bounces under its own weight and in the second it oscillates under its own weight.
The first case angular velocity, spring mass system is
w₁² = k / m
The second case the angular velocity is
w₂² = L / g
They tell us
w₂ = ½ w₁
Let's replace and calculate
√ (L / g) = ½ √ (k / m)
L / g = ¼ k / m
L = ¼ k g / m
