The compressed spring of a dart gun has potential energy of 50 J. If the spring constant is 200 N/m, what is the displacement of the spring?

Spring potential energy is given by U = ½kx². Substituting 50 J for U and 200 N/m for k gives x = √(2U/k) = √(100/200) ≈ 0.71 m. The displacement is about 0.7 m, choice C.

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