On Monday during physics class, we were asked to create a “top” that would spin for a long period of time. The materials we were given included two small paper plates, a pencil, six pennies, and tape. At the end of the lab experiment, we were asked to answer the following questions in a blog post:
How did today's opening activity relate to the engineering design process?
The engineering design process involves designing, building, and testing something. This relates to what we did in class because we had to brainstorm solutions to the given problem, and then we built, tested, and redesigned various models. For example, we tried moving the pennies closer to the center of the plate, and then we tried moving them farther to the outsides. We also experimented with moving the plates farther up and down the pencil. Unfortunately I carelessly poked a hole through the plates that was off-center and this impacted our results. Oops!In the end, we learned that the task would've been much easier if we had snapped the pencil in half.
How did today's opening activity relate to moment of inertia and angular momentum?
If friction did not exist, the top could keep spinning forever. But because there is friction, you want to maximize the angular momentum of the top so that it takes longer for friction to stop the top. You can increase angular momentum by increasing pieces of rotational inertia such as mass and how far away the mass is from the center (or the radius). We did this by putting all six pennies evenly spaced on the outside edges of the plate.