A thin string is wrapped around a cylindrical hoop of radius R and mass M. One end of the string is fixed and the hoop is allowed to fall vertically starting from rest, as the string unwinds. a)Determine the angular momentum of the hoop about its CM as a function of time. b)What is the tension in the string as a function of time. I'm having a hard time even picturing this and how the hoop would rotate as the string unwinded. Some hints would be really helpful, thanks.