Why Things Keep Moving or Stay Still

Have you seen a ball sitting still on the ground? It will stay there unless something pushes or pulls it. This is Isaac Newton's First Law of Motion. This law helps us understand how things move or stay still.Newton's First Law has two main parts. First, an object that is not moving will stay not moving. A book on a shelf will sit there until a push or a pull makes it move.Second, an object that is moving will keep moving in the same direction and at the same speed. It will do this unless a push or a pull changes it. Imagine rolling a toy car across a very smooth floor. It would keep going! On Earth, things usually slow down because of friction or air. These are forces, like small pushes or pulls, that work against motion.So, what does this law mean? Objects like to keep doing what they are already doing. If they are still, they want to stay still. If they are moving, they want to keep moving. To change an object's motion – to make it start, stop, speed up, slow down, or turn – you need a force. A force is a push or a pull.