i am doing a study on the flight dynamics of a sailplane. How does the downward motion of the glider gives rise to lift and the forward thrust. the free http: //www.yorksoaring.com/whatissoaring/wis3.html So the question that has been bothering me is that whether the direction of drag is directly opposite to the the thrust acting on the plane, or is it opposite to the resultant vector from the thrust and lift on the plane, and in this case not parallel to the thrust? In this diagram, the flight path is taken to be in the same direction as the thrust force, i just want to clarify the correctness of such a diagram, as it will affect the answer to my first question. Lastly, i would like to affirm that the thrust force arises from the parallel weight component of the plane right? or is it otherwise?