3.20 Consider a collar of mass m sliding on a frictionless shaft, as depicted in Figure 3.44. The collar can slide along the shaft and is connected to a spring of spring constant k, the other end of which is connected to the pivot point O a distance / from the shaft. The unstretched length of the spring is 7. a. How many degrees of freedom are there in this problem? b. Find the equation of motion for the collar. C m Figure 3.44 Problem 3.20: Sliding collar on a spring.