The unstretched length of the spring is 0.15 m
Explanation:
Given-
Length of the stretched spring, [tex]x_{f}[/tex] = 20 cm = 0.2 m
K = 200 N/m
U = 0.25 J
unstretched length of the spring, x₀ = ?
We know,
U = [tex]\frac{1}{2} (k)[/tex] (Δx)²
Δx = [tex]x_{f}[/tex] - x₀
Δx = 0.2 - x₀
0.25 = 100 (0.2 - x₀)²
0.0025 = (0.2 - x₀)²
0.05 = 0.2 - x₀
x₀ = 0.15 m
Therefore, the unstretched length of the spring is 0.15 m