An air puck of mass m1 = 0.21 kg is tied to a string and allowed to revolve in a circle of radius R = 0.8 m on a frictionless horizontal table. The other end of the string passes through a hole in the center of the table, and a mass of m2 = 0.9 kg is tied to it (see the figure below). The suspended mass remains in equilibrium while the puck on the tabletop revolves.
(a) What is the tension in the string?
____N
(b) What is the horizontal force acting on the puck?
____N
(c) What is the speed of the puck?
____m/s