An object of mass M₁ travels in a circular path of radius R on a horizontal table. The object is attached to a string that passes through a hole in the center of the table. An object of mass M₂ is attached to the other end of the string and hangs vertically under the table, which produces a force on M₁. All frictional forces are considered to be negligible. Which quantity or quantities must be measured to determine the tangential speed required to keep the system in equilibrium?