The First Law states that if a body is at rest and the forces acting on it are balanced then the body will remain at rest. However if the body is moving and the forces acting are balanced then the body will keep moving at constant speed in a straight line. Newton's Second Law is concerned with unbalanced forces. Unbalanced forces produce acceleration. The bigger the unbalanced force the bigger the acceleration.
More questions Here are three diagrams showing the forces acting on moving things.
Answer the questions next to each diagram. An aircraft is flying due north at a constant height and steady speed. The question gives us clear information about the motion. Make sure you always look out for clues given in the question. The aircraft's motion is steady speed in a fixed direction.