What is the main by-product of lift in aviation?

Induced drag is indeed the main by-product of lift in aviation. When an aircraft generates lift, it does so by creating a pressure differential between the upper and lower surfaces of the wings. This pressure difference is a result of the airflow over the wings, which facilitates the lift necessary to keep the aircraft airborne.

As lift increases, induced drag also increases as a consequence of the physics of flight. Induced drag specifically arises because of the vortices that form at the wingtips as a result of high-pressure air spilling over to low-pressure areas. This phenomenon is a direct result of lift generation, meaning that the production of lift inherently leads to a corresponding increase in induced drag.

In contrast, the other options address different forces and factors in aviation. Weight is a force acting downward due to gravity, thrust is the forward force generated by engines, and gravity is a natural force that pulls objects toward the Earth. While all these elements play crucial roles in flight, they are not by-products of lift in the same way that induced drag is. Thus, understanding the relationship between lift and induced drag is key to comprehending the dynamics of flight.