Otherwise known as the Law of Inertia, Newton's First Law states: an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. Here's an example: a ball on the ground. The forces are balanced, the floor is pushing up, and gravity is pulling down.
Now, let's say you pick it up: the forces become unbalanced, since gravity can no longer pull the ball down against the force of your muscles.
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