original_query: What causes the wheel to pivot at one end of its axle?
query: What causes a spinning bicycle wheel, held at one end of its axle, to pivot?
answer: When one hand is removed from the axle, the wheel's tendency to topple is resisted by its spin.  The inertia of the spinning molecules causes a reactive force 90 degrees ahead of the direction of the initial toppling force, leading to a pivot around the supported end of the axle.