How does the Jet engine reaction would help in getting the motion?

Jet Engine get its forward motion because of the reaction of the exhausted high speed gases.But for giving reaction there should be some medium at the rear end. In air it is OK that air is itself a medium to push the engine forward. But I have heard that rocket engine even work in the vacuum. In vacuum what pushes the rocket engine forward if there is no medium in which the exhausted gases are pushed.How does the Jet engine reaction would help in getting the motion?Consider Newton's third law of motion - every ACTION has an opposite and equal REACTION.



Burning of jet fuel with in a jet engine has the ACTION of emitting the "exhaust gases" in one direction. The REACTION is the jet engine moving in the opposite direction, which is known as thrust. It is measured in EPR (exhaust pressure ratio), which is the difference in pressure between the front (intake) and the rear (exhaust) of the engine.



Imagine standing in a small boat with a big rock. If you throw the rock, what is going to happen to the boat? It is going to move in the direction opposite of where you threw the rock. That is a good example of an ACTION (throwing the rock) and a REACTION (the boat moving in the opposite direction), and applies to the thrust generated by a jet engine. The bigger the rock and the harder you throw it, the more the boat is going to move, even though you are not physically "pushing" against any solid medium.



Very little thrust is generated by the exhaust pressure against the medium of the atmosphere, as there just isn't enough mass in the atmosphere - especially at 35,000 feet! Same applies to a rocket engine in the vacuum of space.How does the Jet engine reaction would help in getting the motion?
Say what???? I think what you're trying state is that the expanding gasses need something to push against to propel a rocket forward. And they do you're just not looking at it correctly. In the vacuum of space a rocket engine produces thrust by the rapid expansion of combustion. This expansion is directed out through the rocket nozzle. Thrust is achieved by the equal and opposite reaction of an action (expanding gasses). The gasses go one way, out the nozzle, and this pushes the engine the other way. The gasses do not need some external medium to collide with. Let me think of a good analogy. It's like a toy water rocket. You pump it up with just air and it will just pop off the launcher about a foot, fizzle, and drop to the ground. Air has little mass so there is not much reaction energy. Now, add a little water to the rocket then pump up a air charge behind it. Water has considerable more mass than air thus much more reaction energy. Now the air charge will push the water out the nozzle and produce more reaction forcing the water rocket hundreds of feet into the air. Both air and water charges in this demonstration are pushing against air as you stated in your question but water will prevail. So as you can see it has nothing to do with the collision of materials behind the engine, it is reaction energy that produces thrust.How does the Jet engine reaction would help in getting the motion?I think you misunderstand the concept of jet propulsion. The ability of a jet to generate thrust is entirely related to the jet acting on the components of the engine (momentum transfer), not the surrounding medium (if any). The main component of thrust from most engines is derived from the velocity and mass flow rate of the jet. A minor component will be generated if the jet is at a higher pressure than the surrounding medium (this is called pressure thrust). Again, note that pressure thrust does not require an atmosphere, a rocket engine in space (essentially zero pressure) can also generate pressure thrust.How does the Jet engine reaction would help in getting the motion?
the ancient Greeks though air behind the arrow had to "push it forward"



in the 1650s Newton and others understood that things that are moving CONTINUE to move unless something some Force changes the motion



gravity pulls down. the air across the wings moves down and the REACTION of the air against the wing pushes up to balance



a Propeller is a rotating wing, it pushes air back and the air pushes the propeller forward



A rocket is a container with burning fuel. the exhaust material moves backward and the container moves forward.. It DOES NOT PUSH against the outside air. that is why it works in space



in physics is is called Conservation of Momentum or action and reaction



Most people get confused about this. if you take a science class, especially physics it becomes understandable



e-m my icon if you have more Q. it takes some explanationHow does the Jet engine reaction would help in getting the motion?The law of action and reaction works even in a vacuum. It doesn't need anything to "push against." That's why it works for rockets. And it works for jet engines, too, and doesn't depend on surrounding air.