We started class by talking about what it means for an object to have momentum. The kids knew it had to be moving and they also knew that a massive semi truck moving at the same speed as a small car is going to have more momentum. So right there we have it all, momentum increases with speed and with mass. First we did the Real Science Odyssey Physics (RSO) lab, Giving the Gift of Momentum, where the kids thought about what would happen when they rolled a marble down a track into another marble that is sitting at rest. Then they did the experiment and recorded what happened. They then thought of other experiments to do, basically different collisions between marbles of different sizes, different numbers of marbles, or having them moving at each other. Instead of using cardboard tubes the kids made paper marble tracks and taped them together. I had thought we might be able to spend some time making a paper roller coaster from the templates I had bought last summer, but when my son and I built one the day before class we found it took too much time. It wasn’t too hard, but it just takes more time than we have in one class, especially with younger kids.
Using the glider carts on the air track we repeated some of the marble experiments but with no friction it was much cleaner – the first cart comes to a stop as it transfers all its momentum to the second car.
Then we went outside to complete the second part of the RSO lab, where you drop balls individually and then stack them on top of each other with the smaller, lighter ball on top. Here are the videos from our class doing the experiment.
Physics Girl has a great video that explains why this works, so after we finished trying it ourselves we came in and watched this:
We also watched the first half of this video on the physics of car crashes,
and this lego stop motion movie about Newton’s Laws.
We also played with a Newton’s Cradle all through class and discussed how it was transferring momentum during collisions. Next week, Newton’s 3rd law.