The inertia system provides a common platform and application-programming interface (API) for applications to extend the input received from various multi-touch hardware devices to simulate real-world behavior of application objects. To move naturally, application objects should exhibit physical characteristics such as elasticity and deceleration. When a user lifts all contacts from an object, the inertia system provides additional manipulation events to the application so that the application can handle the events as if the user was still moving the object with touch. The inertia system generates the events based on a simulation of the behavior of the objects. If the user moves an object into another object, the inertia system simulates the boundary characteristics of the objects. Thus, the inertia system provides more realistic movement for application objects manipulated using multi-touch hardware and the API provides a consistent feel to manipulations across applications.