Vector projections

This applet aims to demonstrate visually the projection of a vector u onto a vector v. The bold line is the result of that projection.

The notion can be likened to having a light source perpendicular to $\bf{v}$, in which $\text{proj}_{\bf{u}}({\bf{v}})$ can be seen as the shadow of $\bf u$ cast onto $\bf v$.

Other resources:

Geogebratube page for this applet