This video explains where detrimental induced drag force comes from and how to design airplanes to minimize the induced drag. An experiment is shown to demonstrate how taking steps to reduce the induced drag force acting on a glider increases the distance it can fly.

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Timecodes
0:00 Intro
1:40 Where induced drag comes from
5:48 The induced drag coefficient
6:50 The aspect ratio
8:19 Aspect ratio demonstration
9:36 The Oswald span efficiency factor
10:51 Tapered wings
12:11 Winglets
13:20 Ground effect
14:17 Conclusion