How does inertia work with Newton’s first law?
Quick Answer
Inertia is an object’s tendency to keep doing what it is already doing. Newton’s first law says motion only changes when a force acts on it.
The Full Story
Newton’s first law, published in 1687, states that an object at rest stays at rest and an object in motion stays in motion at constant velocity unless acted on by an external force. Inertia is not a force itself; it is the resistance to changes in motion. A heavier object has more inertia because it is harder to speed up, slow down, or turn. This principle helps explain why seat belts matter, why planets keep moving in space, and why hockey pucks glide so smoothly on ice. It is one of the foundations of classical mechanics.
Key Facts
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