**PURPOSE: **To illustrate aspects of vector algebra.

**DESCRIPTION: **To provide quantitative examples, project a grid on the blackboard and read off coordinates. Demonstrate coordinate invariance by translating and rotating the grid while **A+B=C ** is preserved by leaving the arrows fi
xed on the board.

**SUGGESTIONS: **This demonstration is for the lecture halls where magnetic vectors stick to the magnetic blackboards.

**REFERENCES: ** (PIRA
unavailable.)

**EQUIPMENT: **Overhead projector with transparencies, magnetic vectors.

**SETUP TIME: **None.