Which of the following is a force that propels an unmanned aircraft forward?

Thrust is the force that propels an unmanned aircraft forward. It is generated by the propulsion system of the aircraft, such as engines or rotors, and is essential for overcoming the drag force that opposes the motion of the aircraft through the air. Thrust moves the aircraft in the direction of travel, allowing it to gain speed and altitude. This is particularly critical in unmanned aircraft systems, where efficient thrust generation is vital for performance and maneuverability.

In contrast, drag refers to the air resistance that the aircraft encounters as it moves, while weight is the force exerted by gravity, pulling the aircraft downward. Lift is the upward force that allows the aircraft to rise off the ground and is generated by the wings or rotors. While all these forces play important roles in the flight dynamics of an unmanned aircraft, it is thrust specifically that is responsible for propelling the aircraft forward.