FIGURE P6.20 An air puck of mass my is tied to a string and allowed to revolve in a radius hori- e ot On a zontal table. The other end of the string passes through a bole in the center of the table, and a mass r is tied to it (Fig. P6.38). The suspended mass re mains in equilibrium while the puck on the tabletop revolves. (a) What is the tension in the string (b) What is the central force acting on the puck? FIGURE P6.38