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Parallel Axis Theorem

Definition

The parallel axis theorem states that for an object rotating about an axis parallel to but not passing through its center of mass, its moment of inertia can be calculated by adding together two components - one component being its moment of inertia about an axis through its center of mass, and another component based on its mass and distance from that axis.

Analogy

Think about playing with a see-saw. If you have two people sitting at different distances from the middle, their weights affect how easy it is to balance. Similarly, when calculating moment of inertia using parallel axis theorem, we consider both how mass is distributed around an object's center and how far each piece is from that center.

Related terms

Moment of Inertia: Moment of inertia measures an object's resistance to changes in rotational motion. It depends on both mass distribution and shape.

Center of Mass: Center of mass refers to a point where all parts' masses are evenly balanced. It acts as if all mass were concentrated there for certain calculations.

Rotational Motion: Rotational motion refers to movement around an axis instead of in a straight line. It involves concepts like torque, angular velocity, and angular acceleration.