So try this. Instead of trying to come up with the right answer (and rewarding that), require students to come up with 3 “crazy ideas” for what is happening . A crazy idea (for the earlier experiment with the horizontal and vertical motion) could be that there’s a magnet in the cart. Or that it has a tilted trigger. Or that the ball doesn’t know that it’s moving horizontally when it’s moving vertically. What a crazy idea! Reward students for coming up with these “crazy ideas” and practice shooting them down. Redefine success in your classroom! “Success” isn’t coming up with the right answer, it’s the ability to come up with alternative explanations and come up with the experiments that would shoot them down.
If you don’t believe that process is important, or if you believe that you can tell your students the right answer (and they’ll learn it), then you won’t see the value in this. This is just one example of how our underlying theories of how people learn affect our approach to teaching.
This can be a quick 20 minute exercise in high school or a big introductory undergraduate course. When do you do this? At the beginning of a major topic that uses the idea in question, so head off misconceptions before teaching.