Which jar rolled faster along the table top?
Here's how kids have voted so far:
31% the air-filled jar
44% the water-filled jar
23% they rolled at the same speed
How's it work?
The water-filled jar gets to the bottom of the ramp first, but things start to change when the jars reach the tabletop. The water in the jar rubs against the jar walls, slowing it down. The air-filled jar doesn't experience this friction, and zooms ahead.
Want to talk about it? Go to the boards and discuss your results with other DFTVer's!