Iii) The limit of proportionality of the spring is reached at an extension of 50mm. Continue the graph in Fig. 1.1 to suggest how the spring behaves when the stretching force is increased to values above 125 N.

iv）Another spring has a smaller value of k. This spring obeys Hooke’s law for extensions up to 80mm.
On the grid of Fig. 1.1, draw a possible line of the variation of F with x for this spring.

With the simplified model of the eye, what corrective lens (specified by focal length as measured in air) would be needed to enable a person underwater to focus an infinitely distant object? (be careful-the focal length of a lens underwater is not the same as in air! assume that the corrective lens has a refractive index of 1.62 and that the lens is used in eyeglasses, not goggles, so there is water on both sides of the lens. assume that the eyeglasses are 1.90