As the carbon dioxide is forced out of the back of the extinguisher it puts a force on the tester sitting on the skateboard causing him to accelerate.  (or that’s the theory 🙂  The reason it fails in the experiment is because the carbon dioxide didn’t accelerate fast enough to overcome the friction of the skateboard.  When a space shuttle takes off it has a thrust equivalent of about 30 million Newtons.

Ok next once the space shuttle has taken off it thrusts at an initially slower speed.  Once more fuel is burned, enough to have lift off, it becomes much lighter and can increase in velocity.  This is a result of Newton’s second law a=F/m.  And on a side note, we think of the space shuttle going vertical but once it enters a certain area of the atmosphere it turns horizontal and most of the acceleration happens there!

Enjoy the video as the jetski pump makes this jetpack work on 1800 Newtons of thrust!