A 0.500kg mass is attached to a massless string of length 25.0 cm that breaks if it under at least 50.0 N of tension. The

 A 0.500kg mass is attached to a massless string of length μ25.0 cm that breaks if it μunder at least 50.0 N of tension.  The system undergoes circular motion in a vertical plane.  What is the minimum speed of the mass at the top of its motion that would cause the string to break at the bottom of the mass motion?