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Name: Bryant
Status: student
Grade: 9-12
Location: TX 
Country: N/A
Date: 7/1/2005


Question:
On a fighter jets engine theres a maneuverable nozzle that can open up and close up. On a few web sites I have been using to learn about jet engines it states: the bigger the nozzle gets the more thrust it produces. But I figured it would be more like a water hose - when you pinch off the end the pressure rises and the water is put under more force, which one of us is right? Now granted that if the nozzle is not large enough, and it stays closed for too long, it will destroy the engine from all the back pressure and strain.


Replies:
One thing to consider is that the amount of hot gas leaving the back of the jet engine is not at a constant level, like a hose. The nozzle responds to differences in throttle, and acts to optimize the thrust produced at any throttle setting.

Consider your garden hose turned all the way on. Just a slight restriction on the opening will allow you to spray water a good distance. Too much restriction, and you still get the high pressure water stream, but restricted it to a fraction of its flow.

Now consider the same hose turned almost all the way off. No restriction on the open end of the hose and water just falls out in a dribble. Cover most of the opening with your thumb though, and even with just a little water actually flowing through the hose, you can spray it a small distance.

Ryan Belscamper



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