I have loved using the interactive student notebooks this year! To introduce linear relationships we looked at how tennis balls bounce when dropped from different heights.
See the ISN in the background?! Love! The students graphed their results and then we talked about it. It really helped them begin to see the relationship and it was a great introduction to slope.
The left side was the tennis ball data and graph (it opens up to a full page). The right side was our thinking page for all the things we know about slope. The tennis ball activity gives me a reference point to go back to during the slope unit.