When they either laugh or think I am trolling I ask them to change my mind by refuting this observation. I also tell them that I have a first hand observation while they have some vague, hand waving pictures of trajectories.
The discussions with some get interesting when they slowly discover the concept of center of mass, relative movement etc.
Children are better at that because they do not have yet opinions burned into their brains by weak schooling (schooling which prefers to drop equations than let them discover things as they go).
I have a PhD in physics so it is easier for me (and people do not assume that I am an excited flat earth believer or somethkng) but I am really sad that a lot of things which people are told are just that: told. Not done through self discovery.