Laboratory / Mathematics
Vectors and coordinate change
Compose two draggable arrows and compare component addition with the head-to-tail construction. Then rotate the coordinate axes and watch the coordinates move while the resultant arrow stays fixed.
What changed
The same resultant combines a horizontal write of 5 with a vertical write of -15. The components describe the arrow; they are not the arrow itself.
Return to the route
Experiment after prediction.
Before changing a control, say which visible feature should move and which should remain invariant. That prediction is the useful part of the experiment; motion alone is not evidence.