Data structures and algorithms for contact detection in numerical simulation of discrete particle systems

A foldable three-wheeled jogging stroller having a lower frame assembly including an axle for supporting two rear wheels, the axle having a pivotally coupled fork assembly to support a front wheel and a pair of fixedly attached upright support tubes. An upper frame assembly includes a U-shaped handlebar having first and second extension tubes each fixedly attached to an interconnect member, each interconnect member configured for hinged attachment of an upright support member and for slidably receiving a first end of one of third and fourth tubes whereby the interconnect member can slide freely along its respective tube to enable an erect upper frame assembly to fold into a collapsed position overlaying the base assembly. The other ends of the third and fourth tubes are attached to a footrest that further has extension tubes coupled to the front wheel support.