A$\mathrm{.}5\mathrm{.}0\mathrm{.}0.$x$.{10}^5.kg.$ subway train is brought to a stop from a speed of $0\mathrm{.}500\frac{m}{s}$ in $0\mathrm{.}600$ m by a large spring bumper at the end of its track. What is the force constant $k$ of the spring $($in $\frac{N}{m})?($Enter a number.$)$

N$/$m

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