Falling Slinky Surprise
The bottom hangs still briefly.
Teaching & key ideas
What you do: Hold it stretched vertically and release the top.
What students see: The bottom hangs still briefly.
Why it works: The release information travels down the spring as a wave.
Question to ask: Why doesn't the bottom fall right away?
Lesson flow
Predict → demonstrate → observe → briefly explain → ask: Why doesn't the bottom fall right away?