newtons law unlawful?

[boobesque]

firstly i am aware that space is not a total vaccum. i am also aware that the particles in space, such as the higgs field boson, random neutrinos etc play little part in interactions with larger matter such as satelites. now when a satelite wants to move, or rather when we want a satelite to move, we fire its rocket engine to push one way or another. if there is nothing for the engines force to interact with how is it moving? it has to push against something

[Hamish]

Newtons 1st law, every action has an equal and oposite resction. If I (100kg) thow 1kg of gas at 100km/h in one direction - under ideal condition (no other forces acting on me) I will move in the opposite direction at 1km/h. The effect is similar to the recoil of firing a gun.

[fo3nix]

Firstly, the Higgs boson field is just some theoretical thing. It's not been seen yet.

The reason, as Hamish sort of explains, is change of momentum. Momentum is mass * velocity, and so changing one of these changes the momentum. Thus, when a rocket kicks out particles of fuel at the back it's losing mass and so its momentum changes.

The key thing here for a simple understanding is Newton's second law. This states that force is equal to the rate of change of momentum. So since the momentum is changing for the rocket, the rate that it's changing by gives a force.

F=ma
F=m(d/dt)(v)
F=(d/dt)(mv)
F=(d/dt)(momentum)

The (d/dt) bit is the differential.

[dawkins]

that is newtons 3rd law Hamish but that appart you are spot on..

the following link explains all boobesque:

http://www.grc.nasa.gov/WWW/K-12/TRC/Rockets/r ocket_principles.html

[Space]

The engines push against the gas that is coming out of them.

[Hamish]

Oops can't count.