Just read the text books. Don't get confused between compressible and incompressible. It alters things a bit, but not the fundamentals. These engines/motors are momentum change devices, and they rely on Newton's Laws of motion.
Also, if the hose were in a straight line, the force would still be there, but the hose would be restrained by the body of the hose itself!
All the basic equations of thrust, as shown in previous threads, relate to mass flow, and the exhaust velocity and the forward velocity, and the density, and things that affect density, like temperature (remember the thread about water injection - it's a bit like an intercooler in a car, it cools the air after compression and raises the density. It also drops the pre-combustion temperature, which increases the change in temperature pre- and post-combustion. This is a fundamental determinant of thermodynmaic efficiency).
Don't take my word for it, read a physics text book, or "The Jet Engine" by Rolls-Royce.
Also, in terms of the original question, am I right in thinking that the combustor of an RR Trent 700 or the like is working at a rate of something like 170MW (I'm not so sure about this - I read it on the back of a matchbox) - try relating that to a power station or the power consumption of a town.