What force provides the forward motion necessary to move a glider through the air?

• A. Gravity
• B. Lift
• C. Drag
• D. Thrust

Answer: (A)

Forward motion for a glider without an engine comes from gravity. When a glider is released, gravity pulls it downward; as it descends along its flight path, gravity has a forward component that accelerates the aircraft through the air, creating the needed airspeed. That airspeed is what enables lift to support the glider and keep it in flight. Lift acts upward and opposes weight, drag resists the forward motion, and there is no thrust pushing the glider forward in a typical unpowered glider. So gravity is the force that generates the forward motion.