Rocket engineers use Newton's third law during launch. Identify the action force.

Question

anonymous · Answer

• Exhaust gases push down on the earth.
• Rocket travels upward.
• Earth pushes back on the exhaust gases.

plainntall · Answer

What does Newton's Third law say?

anonymous · Answer

A force is a push or a pull upon an object that results from its interaction with another object.

anonymous · Answer

This means that for every force there is a reaction force that is equal in size, but opposite in direction.

plainntall · Answer

Exactly.  What force is acting on the rocket?

anonymous · Answer

The ground force, Which is earth?

plainntall · Answer

Not exactly, the rocket is pushed up by the exhaust gas which means the rocket pushes the exhaust gas down.

anonymous · Answer

So its the exhaust gases pushing down on the earth?

plainntall · Answer

Rockets work in space as well as on Earth.  that is because it is the molecules of the exhaust gas pushing on the rocket and the rocket pushing on the molecules of the exhaust gas that makes it go.  The exhaust gase/earth system has nothing to do with the thrust of the rocket.

anonymous · Answer

So basically its all about the the rocket going upwards?

plainntall · Answer

Who ever wrote your questions seems to be confused..  I think they want you to say that the exhaust pushing on the earth is the action force and the earth pushing on the exhaust gas is the reaction force., but that isn't part of the rocket system.

plainntall · Answer

Your answer of 
So its the exhaust gases pushing down on the earth
is correct for the exhaust gas/Earth system, but rocket engineers wouldn't really care about that since it is the exhaust/rocket system that is important.

anonymous · Answer

Okay, So im gonna try that out and talk to my instructor tomorrow to see whats wrong with the wording?

plainntall · Answer

Regardless of the wording you seem to have a good feel for what the action force is and what the reaction force is.  :)

anonymous · Answer

Haa, Yeah. Its just I get confused on this sometimes, So id rather ask then not say anything? But thanks again.

08surya · Answer

exhaust gases and gravity are action and reaction fores

plainntall · Answer

I don't think they are.
The gravitation force of the Earth on the molecules has a reaction force of the gravitational force of the molecules on the Earth
The electromagnetic force of the Earth surface molecules on the exhaust gas molecules has a reaction for of the electromagnetic force of the exhaust gas molecules on the surface molecules of the Earth.  The two graviational forces and van der wall forces of the molecules are action-reaction pairs, but gravitational and van der wall electromagnetic forces aren't.

08surya · Answer

sry i think its exhaust gas and gravitational force.
everything which comes inside earth face gravitational force.