Step 1: Ever tried to balance a pencil–standing on its tip–on the pad of your finger? Not so easy, is it? Add to that a folding pocket knife and the task becomes nearly impossible–or so you would think. But we’ll prove to you that it is, in fact, an easy task. So easy that you can do it dancing.
Step 2: Secret: unfold the knife as shown.
Step 3: Push the knife blade into the pencil just above the pencil’s tip.
Step 4: Place the pencil on the pad of your finger. It stands easily without any effort on your part.
Step 5: Now move your hand quickly back and forth. The pencil sways and spins, but doesn’t fall! Why? The center of gravity of the combined object (pencil and knife together) is now lower than its resting point–the pad of your finger, in this case.