<iframe width="580" height="385" src="https://www.youtube.com/embed/COt_uDqNs4Y" frameborder="0" allowfullscreen></iframe> <br>As part of their aerodynamics until students created their own helicopters with the four forces of flight in mind: thrust, drag, ... <br><a href="https://www.youtube.com/watch?v=COt_uDqNs4Y">source</a>
