Rockets Propelled In Space According To Newtons 3Rd Law... Read Details

[Sachin114]

Every act has eq and opp reaction. Or every force(Say x) has eq and opp force(say y). Now, is there any difference between x and y other than their direction. If no then... Y is also a kind of force... will it have an equal and opposite force... If yes then how are rockets propelled in space? Again i can feel deep within that this is a stupid one... so forgive me... thank you...

[waterboatman]

There is no atmosphere in space, so there is no resistance to the rocket force, hence a rocket pointing the other way is required to act as a brake.

[Old_Geezer]

Exhaust moves out in one direction. The opposite force moves the rocket in the opposite direction.

[waterboatman]

Put a bit better than I did OG. ;o}

[Sachin114]

"When a rocket shoots fuel out one end, this propels the rocket forward — no air is required" this is taken from http://www.livescience.com/34475-how-do-space-rockets-work-without-air.html.... Now let us consider the force of rocket shooting fuel out one end be x ( according to our question), and the force propelling the rocket be y... Since none of these forces require air to act so why would the third force (opposite to Y.. lets call it as z) need any kind of resistence (say air) to act...

[Sachin114]

thats right OG... But i am asking that the öpposite force"that you mentioned is also a FORCE in all its entirety... Will it have its own equal and opposite force??? Hope i am not confusing you my friend...

[Old_Geezer]

y is opposite to x
I'm unsure what this air dependent z is

[waterboatman]

It's own opposite force is the original rocket force.

[Sachin114]

I have given a name to the third force as z which if its there would be acting oppiste to y.... OG i totally understand what you are saying... Its quite intuitive... But only if i could make my question more clear... OK let us assume for a while the y force to be the primary force acting in one direction(Just imagine)... Then will it have a opposte force....

[Sachin114]

ok... so is this right... y eq and opp tox , and x eq and opp to y... if both are eq and opp then how could the rocket propell as they both will cancel each other out... m i wrong somewhere waterboatman?

[EDDIE51]

Newton's third law states >>
'To every action, there is an equal and opposite reaction'
So the 'reaction' propelling the rocket forward is exactly equal and opposite to the 'action' of the expelled exhaust.
Atmosphere plays no part in the this. It just causes some resistance due to friction that absorbs some of the energy of the 'reaction'. So a rocket is more efficient in a vacuum. It is a common mistake that a rocket exhaust needs something to 'push against' but this is untrue.

[waterboatman]

You are indeed. but understandably so. What you have forgotten to take into account is that there is no atmosphere in space, so no resistance to the rocket thrust, hence another rocket mounted at the front is required to provide the braking force.

[waterboatman]

You're right eddie. I was trying to simplify the question.

[Sachin114]

Thank you guys...

[Old_Geezer]

They don't cancel out. One drives the fuel/exhaust the other the rocket. They are not pushing against each other but pushing away from each other.