Inertia is the property of opposing an external influence or force that changes its state of inertia. When a body is at rest it continues to so.
Momentum is mass * velocity. As long as the object with a uniform velocity continues do move in the same direction (and with same speed), the momentum remains constant. Momentum does not change unless there is an external force on the body forces the body to change its velocity.
Inertia is the resistance of an object to change its state of motion, directly related to its mass, while momentum is the product of mass and velocity, describing the motion of an object. Both concepts involve mass and illustrate resistance to change in motion. Understanding both is crucial for grasping how forces affect moving and stationary objects.
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