# Day 109: Building the Momentum Transfer Model

**Posted:**April 10, 2014

**Filed under:**School Days |

**Tags:**MTM, paradigm Leave a comment

For a few years now I’ve been building the momentum transfer model using an empirical approach, but this year I decided to have students try to derive conservation of momentum first. I did this for two reason; first, time (we have had 6 snow/cold days this year). Secondly, I also did this for time reason during projectile motion, and I found that students really like the idea that they can use their prior knowledge of models to figure out something new.

To do this I walked around and asked groups lots of questions, guiding them to get to conservation of momentum. Once groups got to the point of attempting free body diagrams, I had a group present and we had a great time re-learning Newton’s 3rd Law (it’s still amazing to me how strongly their misconceptions are rooted: “but if one has a bigger mass, it MUST exert a bigger force!”). From there students went back into groups to finalize, and we had presentations at the end as well, particularly to discuss why the change in time must be the same for both objects.

##MTM, ##paradigmlab