Centripetal force is easily calculated as long as you know the mass, m, of the object; its distance, r, from the center; and the tangential velocity, v. This equation is based on the metric system; note that the centripetal force, f, is measured in Newtons. 
  
 F = mv^2 / r
 19 N = m ( 0.54^2) / ( 0.36)
 Solve for m
 M = 23.5 kg