A conical compression coil spring, as illustrated in Figure 12.6, is made of 3-mmdiameter steel wire and has an active coil diameter that varies from 20 mm at the top to 45 mm at the bottom. The pitch (axial spacing between corresponding points on adjacent coils) is 7 mm throughout. There are four active coils. A force is applied to compress the spring, and the stresses always remain in the elastic range.
(a) As the force is increased, which coil deflects to zero pitch first?
(b) Calculate the magnitude of force required to cause the deflection in part a.
(c) Suppose the force is increased until the entire spring is compressed solid. Neatly sketch a force-deflection curve for the spring.