*In this paper, we study the quasi-static motion of an elastically suspended, unilaterally constrained rigid body. The motion of the rigid body is determined, in part, by the position controlled motion of its support base and by the behavior of the elastic suspension that couples the part to the support. The motion is also determined, in part, by contact with a frictional surface that both couples the rigid body to the unilateral constraint and generates a friction force. The unknown friction force, however, is determined in part by the unknown direction of the rigid-body motion. We derive an analytically solvable set of equations that simultaneously determines both the friction force and the resulting rigid-body motion.*

*We also address the issues of whether a solution to these equations exists and whether the obtained solution is unique. We show that, for any passive compliant system in which the nominal motion imposes contact, a solution to the set of motion equations always exists. We also show that, for any passive system with an upper bounded friction coefficient, the solution is unique. Two sufficient conditions that guarantee the uniqueness of the solution are presented.*

*(NMc/utina bruchi *Hustache, and *N. eichhQrnUu *Warner) necessary to initilialize the INSECT model which simulates the biological control of waterhyacinth by the weevils. The objective is to estimate the initial input values for the adult population so that the sum of the absolute differences between the observed and the simulated numbers of weevils is minimized. In general, the simulated values using the initial values obtained from the mathematical programming problem were within the 95% confidence intervals of the actual field observations. Also, in many cases, the simulation results indicated trends similar to those indicated by the field data in both timing and the numbers of weevils.