Answer
Energy conservation leads to
$$
K_{i}+U_{i}=K_{f}+U_{f} \Rightarrow 0+m g h_{0}=\frac{1}{2} k x^{2}-m g x
$$
$\text { which (with } m=0.70 \mathrm{kg})$ yields $h_{0}=0.86 \mathrm{m}$
Work Step by Step
Energy conservation leads to
$$
K_{i}+U_{i}=K_{f}+U_{f} \Rightarrow 0+m g h_{0}=\frac{1}{2} k x^{2}-m g x
$$
$\text { which (with } m=0.70 \mathrm{kg})$ yields $h_{0}=0.86 \mathrm{m}$
