(eng): The paper describes a simple time-optimal control strategy for a class of secondorder bilinear systems with nonnegative inputs. The structure of the model is motivated by the task of noncontact manipulation of an object in a planar force field generated by a single source, such setup constitutes a basic building block for a planar manipulation by an array of force field sources. The nonnegative-in-control property means that an object (particle) placed freely in the field can only feel an attractive force towards the source. In this paper we further restrict the control inputs to a binary signal-the field can be switched on and off. The control objective is to bring the object to the origin (where the source of the force field is located) as fast as possible. The optimal switching strategy is proposed using geometric arguments and verified using numerical simulations and experiments with a laboratory platform for noncontact magnetic manipulation.