Inertia and Momentum

Inertia is the property of an object that resists changes to its motion; the more mass an object has, the more inertia it possesses. This means heavier objects are harder to start or stop moving. Momentum is the quantity of motion an object has, calculated as the product of its mass and velocity. It indicates how difficult it is to change an object's motion. In rigid body mechanics, understanding both helps us predict how objects will move when forces are applied, whether they're at rest, in motion, or colliding with other objects.