Old 23rd Nov 2012, 19:39
  #64 (permalink)  
Join Date: Jan 2008
Location: Reading, UK
Posts: 10,648
Sorry Dave but you're wrong here.

There are 4 forces acting on a gliding some of the time.

Your nasa illustration shows a gliding falling from the sky, BUT if he builds up some speed ( momentum ) and pulls back on the stick good n hard what happens, well he will go back up again against gravity untill he runs out of velocity at Agogee and then gravity will take over again and he will fall to earth again

During this upwards flight bit he is using the momentum built up as THRUST, and yes its called thrust becuase the momentum is PUSHING the glider upwards against gravity with the kinetic energy being converted to potential energy that is known as height, as is the tension on a kite string that stops it fluttering away in the wind.

so during this upwards flight mode using the momentum as thrust 4 forces are acting on the glider, not 3.
I suggest you Google Newton's Second Law before you dig yourself in an even deeper hole.
DaveReidUK is online now