Physics
Parallel Axis Theorem
Quick fact
The Parallel Axis Theorem allows calculating rotational inertia about any parallel axis using just the moment of inertia about the center of mass and the distance between axes.
Why this is interesting
Ever wondered why a spinning top is stable when it rotates around its center but wobbles if you change the axis? The answer lies in how mass distribution affects rotation.
Read the full explanation
Understanding Parallel Axis Theorem
Imagine holding a spinning wheel by its edge instead of its center. Even though it looks different, the wheel's resistance to rotation depends on how its mass is spread out—this theorem helps quantify that difference for any parallel axis.
A deeper explanation
The Parallel Axis Theorem states that the moment of inertia about any axis is equal to the moment of inertia about a parallel axis through the center of mass plus the product of the total mass and the square of the distance between the two axes. This allows engineers and physicists to calculate rotational behavior without recalculating from scratch, saving time and reducing complexity.