Okay so we have a block attached to a spring with a spring constant of 50 N/m. The spring is in the relaxed state. We apply a force 3N along the positive x direction. The block moves along the x axis,stretching the spring until the block finally stops. What is the block's displacement? When the block is stopped the force of the spring on the block should be -3 Newtons. Using the formula F=-kx I get the answer 3/50=0.06m. The book's answer is 0.12m. What exactly am I doing wrong?