6.An elastic cord used in bungee jumping is normally 10 m long and has spring constant k = 250 N/m. At the lowest point in a jump, the cord length has doubled. How much work has been done on the cord?
(A) 2.5 kJ
(B) 12.5 kJ
(C) 25 kJ
(D) 125 kJ
(E) 250 kJ
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統計: A(2), B(2), C(1), D(0), E(0) #3427006
統計: A(2), B(2), C(1), D(0), E(0) #3427006