Newton's First Law of Motion

Newton's First Law of Motion states that objects in motion will stay in motion unless acted upon by an outside force and that objects at rest will stay at rest unlest acted upon by an outside force. In the case of our balloon car, the car stayed exactly where it was until the balloon's forward force acted on it. Then, when the force of air decreased because there was less pressure in the balloon, the air pushing against the car in the hallway began to slow the car down until it finally slowed to a stop because the forces acting on it were balanced out.