Newton's 1st Law
Object is motion being stopped by an unbalanced force
Law of Inertia states that an object at rest or moving with constant velocity tends to stay at rest or moving with constant velocity unless it is acted upon by an unbalanced force. In other words, objects continue to do what they are doing. If they are stationary, they will continue to be stationary. If they are moving, they will continue to move.
For example: When the baseball is in motion during a game, the baseball will continue to move until the fielder has fielded it and stopped it. The baseball will stay in motion unless acted upon by an unbalanced force which in this scenario was the fielder who received the baseball. This brings the ball back to the initial stage of rest.
The same goes for the opposite. If an object is at rest it will continue to be at rest unless acted upon by an unbalanced force causing the baseball to move. This applies to a batter hitting a baseball off of a tee. The object at rest is the baseball on the tee. It will continue to stay on the tee until an unbalanced force (the batter) makes contact with the baseball causing it to move.
For example: When the baseball is in motion during a game, the baseball will continue to move until the fielder has fielded it and stopped it. The baseball will stay in motion unless acted upon by an unbalanced force which in this scenario was the fielder who received the baseball. This brings the ball back to the initial stage of rest.
The same goes for the opposite. If an object is at rest it will continue to be at rest unless acted upon by an unbalanced force causing the baseball to move. This applies to a batter hitting a baseball off of a tee. The object at rest is the baseball on the tee. It will continue to stay on the tee until an unbalanced force (the batter) makes contact with the baseball causing it to move.