Today in class we were working on practice 3 from my Momentum Transfer Model (MTM) packet (which is a combination of standard modeling questions, Kelly’s questions, and a couple I wrote maybe). In first period we did problems 2 and 3, below, in a row. After problem 3 I gave students one of my standard speeches about how some students decide physics is about choosing an answer and then switching it because they know they’ll be wrong. I try to emphasize a number of times throughout the course that a good scientist isn’t one who’s initial intuition is correct; she is one who is willing to take a step back, consider the science of the situation, and then make sense of it. Anyway, in 1st period, almost every student choose that the VW experienced a greater force in 3a, despite the fact that we did quite a bit of work with Newton’s 3rd law, work I still think is pretty effective, back in November. The problem is, students haven’t made it second nature yet to start with science and end with conclusions. They start with their gut and go from there.
During 2nd hour I inadvertently gave my speech between questions 2 and 3. Every kid said that the forces were equal in 3a. Every kid.
This helped me to realize that even when students understand a concept at some point, they still tend to revert back to gut-first thinking over time. In this case, the students were attempting to make sense of the situation, but without considering the physics involved they tend to confuse acceleration (the affect of the collision) with the force of the collision itself. Instead, if they start by applying Newton’s 3rd law, such that the forces are equal, then apply Newton’s 2nd to show that the effect of that same force depends on the mass of the object, it makes sense that the forces are equal but that the effect, the acceleration, is different.
So it’s not really that big a deal in the scheme of things when students’ don’t correctly analyze a collision, but it’s a much bigger deal when we have policymakers denying climate change. The problem is summed up in a picture from a tweet that came across my feed the other day;
Teaching science should mean giving students the tools to analyze situations and make logical conclusions while at the same time emphasizing how to do so in a variety of situations. If we fail to give students the tools of science, or show them how they apply, or challenge them with different situations, or reiterate their prior understandings, we leave room for them to revert to gut-oriented thinking. I hope that my preaching about starting with science rather than intuition can help in some small way to move our society from one where people try to ‘prove’ their own biases to one where we use data on a real quest for truth.