B. As the suitcase falls the strength of the air resistance force on the suitcase increases with the speed of the suitcase. The strength of the gravitational force on the suitcase remains the same. Eventually, the upward force due to the air resistance (draG. equals the strength of the downward gravitational force, and therefore the forces are balanced. When forces are balanced, the Net force on the suitcase is zero and according to Newton's Second Law, the object moves at constant speed.