Answer
83.9 m
Work Step by Step
You measure the contracted length. Find the rest length from equation 26–3a.
$$\mathcal{l} = \mathcal{l}_{o} \sqrt{1-\frac{ v^{2} } { c^{2} }} $$
$$\mathcal{l}_{o} = \frac{\mathcal{l}}{ \sqrt{1-\frac{ v^{2} } { c^{2} }}} $$
$$\mathcal{l}_{o} = \frac{44.2m}{ \sqrt{1-0.850^2 }} =83.9m$$
