Final answer:
Positive gravity forces, or positive G-forces, in aircraft are experienced during maneuvers like banked turns and pull-ups, where the wings generate additional lift that increases the forces felt by the occupants, illustrating concepts of Newton's first law of motion.
Step-by-step explanation:
Aircraft maneuvers that cause positive gravity forces, often referred to as positive G-forces, occur when the lift force acts in such a way that it increases the weight force felt by the occupants. This is most often felt during banked turns, pull-ups, or when an airplane is climbing. For instance, when an airplane enters a banked turn, the lift force due to the air on the wing acts at right angles to the wing, providing enough lift to counteract the airplane's weight and generate a horizontal component to change the airplane's direction.
Similarly, during a pull-up maneuver, where the aircraft's nose is pitched upwards, the wings push air downwards (utilizing the conservation of momentum), which increases the upward force on the airplane, again leading to positive G-forces.
These sensations can be compared to taking off in a jet, where you feel pushed back into your seat, or making a sharp turn in a car, where you feel pulled to one side. These examples illustrate Newton's first law of motion, which describes the tendency of objects to continue in their state of rest or uniform motion unless acted upon by an external force.