試題詳解

12. A force produces potential U(x) = ax⁴. where a = 1.43 J/m⁴ . What is the force and direction when the particle is at x = -0.78 m?
(A)ON
(B)-0.67 N
(C) 0.67N
(D) -2.7 N
(E) 2.7 N