Imagine a multistage rocket and the changes in acceleration.
Figure 4-3 in https://www.ibiblio.org/apollo/Documents/lvfea-AS506-Apollo1... shows this for Apollo 11.
Figure 4-3 in https://www.ibiblio.org/apollo/Documents/lvfea-AS506-Apollo1... shows this for Apollo 11.
There is an interesting Δa/Δt while fuel is consumed and mass changes.
There are discontinuities to the graph when engines are shut down and stages decoupled.
Over a macro scale, it’s discontinuous, of course.
But, checkout Zeno's paradox for more on your philosophical questions