試題詳解

(3)Stretching a non-linear spring requires an amount of Work given by the equation U = 22x² – 9x³, where U is in Joules and x is in meters. How much force is required to hold this spring stretched out 4.0 m from equilibrium position?
(A)256 N
(B)246 N
(C)278 N
(D)212 N
(E)298 N