One of the major differences between our common Physics models of energy change and realistic models of them is

In the Physics models, the acceleration due to gravity is rounded to a non-exact but easier to use number

In the Physics models, the velocities are only calculated at set intervals of time, instead of continuously

In the Physics models, the objects are assumed to have simplified shapes in order to make motion by acceleration easier to calculate

In the Physics models, we do not take into account the energy change by the friction of moving components