12.1 SOME MATHEMATICAL HABITS OF THOUGHT FOR DESIGN MODELING12.2 SOME MATHEMATICAL TOOLS FOR DESIGN MODELING12.3 MODELING A BATTERY-POWERED PAYLOAD CART12.4 DESIGN MODELING OF A LADDER RUNG12.5 PRELIMINARY DESIGN OF A LADDER RUNG12.6 CLOSING REMARKS ON MATHEMATICS, PHYSICS, AND DESIGN12.7 NOTES