GROSS EARTH & SOLAR SYSTEM STRUCTURE

Find Earth's mass from the acceleration of gravity by two methods: a ball drop using a commercial timer and photogate system, and timing several swings of a pendulum (works as well or better)

Discussing solar system formation, demonstrate conservation of angular momentum using a string connecting two balls threaded through a hole in the base of a cup. We set the upper ball swinging, so as the lower one slides down, the radius of the top one's orbit decreases and it speeds up.

Racing a hoop and disk of the same mass down an inclined plane motivates the concept of moment of inertia, and leads to the idea of using a planet`s moment of inertia to learn about its core density.