The machine

Mr. 7 has been loving his new science teacher and science lab.  They've been studying simple machines and mechanical advantage, and their semester-end project was to build a machine based on one or more simple machines, and explain its function.

Mr. 7 was clear on the design: a pulley attached to a weighted end of a lever.  What was less clear was what it could be used for.  After several brainstorming sessions, he decided it was a kitchen scale: one hangs the water pitcher in the sink, and fills it until the counterweight (the blue-taped batteries or pink weights below) minus the water weight in the pitcher balances out your food (below, a 1 pound can of beans).  His classroom presentation was a success.

Mr. 7's Dad has been wanting a kitchen scale for a while.  We'll have to see how Mom will feel about the scale becoming a permanent fixture.

Honorable mention goes to the Google Cambridge office, who cheerfully debated over e-mail whether iridium or osmium would be a more cost-efficient counterweight while Dad was boringly buying cheap handweights at the sporting goods store.