# Day 18: Intertia & Free Fall

Physical Science: Inertia

After some brief notes on inertia, students did a lab where they played with some examples and practiced using inertia to explain their observations. At the end of the lab, students had a mini-design challenge to come up with a way to keep the passenger safe in a collision. Even though we don’t go into torque in the course, it did get students thinking about where the force is applied. I intentionally left the language in the question vague, and I was pleased with the conversations students had about what it meant to keep the passenger safe.

This group debated about the efficacy of their “seat belt” since the passenger’s “feet” still swung forward in the crash

Physics: Introducing Free Fall

We went to the computer lab for students to use a Direct Measurement Video to begin exploring free fall. This one allows students to watch side by side high speed videos of a variety of objects in free fall. I asked students to find a value for the acceleration of a falling object and to identify any variables that affects that acceleration. While many students were quick to dismiss small differences in the time, one group had a great discussion. They saw that the bowling ball fell noticeably faster than a ping pong ball, so they not surprisingly decided that weight must matter. One person wasn’t satisfied; he played the video of a large steel ball side by side with a small steel ball to show they fell at the same rate in spite of different masses and radii. With some nudging, they were able to agree that density must be the key factor.