You could use the "Contact with Point" element, locating the point at the front-most part of the segway. This element requires the "Fixed Triangulated Surface" be used as the ground.
However, only use the point contact if you need to model the physics of the contact/impact. (I don't think your assignment requires this).
If you just want to stop the simulation when the segway falls over, instead use the "termCond" parameter of the global model parameters (you can access this by double-clicking on the background of the diagram view of the model). Write an expression for termCond such that it becomes true when the segway falls over (e.g. a certain angle exceeds 90 degrees). This will stop the simulation when the expression becomes true.
You could use the "Contact with Point" element, locating the point at the front-most part of the segway. This element requires the "Fixed Triangulated Surface" be used as the ground.
However, only use the point contact if you need to model the physics of the contact/impact. (I don't think your assignment requires this).
If you just want to stop the simulation when the segway falls over, instead use the "termCond" parameter of the global model parameters (you can access this by double-clicking on the background of the diagram view of the model). Write an expression for termCond such that it becomes true when the segway falls over (e.g. a certain angle exceeds 90 degrees). This will stop the simulation when the expression becomes true.