A cart is attached to a horizontal spring fixed to a wall. Rightward is defined as the positive x-direction. The spring is compressed so that the cart is momentarily at x=−0.05m from equilibrium and at rest. Which statement best describes the direction of the spring force acting on the cart at that instant?
a) 0 N, because the cart is instantaneously at rest
b) Leftward, toward decreasing x
c) Rightward, toward increasing x
d) Direction cannot be determined without knowing the spring constant k