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F = 0, (a):, x= 0|, F, is negative, x is positive, (b), F, is positive, xis negative, F-, (c), F,, F,=- kx, Area = -, 2, (d), IB, Fig 6.7 Illustration of the spring force with a block, attached to the free end of the spring., (a) The spring force F is zero when the, displacement x from the equilibrium position, is zero. (b) For the stretched spring x > 0, and F < 0 (c) For the compressed spring, x<0 and F > 0.(d) The plot of F versus x., The area of the shaded triangle represents, the work done by the spring force. Due to the, opposing signs of F and x, this work done is, negative, W, = -lx/2.