Does rocket engines push on air ?

[nec209]

I'm trying to understand Newton's Third Law of Motion: for every action there is an equal and opposite reaction.

 

If a rocket does not push on air than what drives it? Is it internal pressure in the Combustion chamber ?

 

When the gas escape pushes on gas accelerating it backward then the gas must therefore push forward on rocket:eek:

 

The mass have be the same? Small mass cannot move big mass it has be the same mass.

[Mokele]

It's pushes out hot, burnt fuel products.

 

If the gas pushes in all directions, the rocket doesn't move, because the forces are equal. Because there's a hole in one end, the forces are unequal. Take a soda can, shake it up, and it doesn't move. Poke a hole in it, and it zips across the floor, propelled by the ejected liquid and unequal pressures.

 

And small masses can indeed move big ones, if their momentum is high enough. Even fire a powerful gun? Same thing - the mass of the bullet is tiny, but has such high velocity that it means you move back appreciably.

[nec209]

And if it has no where to pushe ? Like if there was no hole on the rocket that what will happen?

 

And small masses can indeed move big ones, if their momentum is high enough.

 

You mean if the mass has enough speed?

[cameron marical]

does the combustion move the rocket by pushing on the base as its escaping?

[D H]

There is a third law reaction here: The exhaust gases push on the rocket itself. A rocket works just fine in the vacuum of space far removed from anything to push on. (In fact, rockets work better in the vacuum of space.)

 

Imagine that you are standing alongside a pile of baseballs on slab of wood that in turn is on a huge air hockey table. Start throwing baseballs horizontally and you will start moving in the opposite direction. To throw a baseball you must exert a force on the baseball to make it accelerate. By Newton's third law, the baseball exerts an equal but opposite force on your hand. That reaction force propagates from your hand to your arms and eventually to your feet and the slab of wood. The slab and everything on it accelerate each time you throw a baseball.

 

The same kind of thing happens with the rocket. Some force makes the escaping exhaust molecules speed up. That same force in turn makes the rocket speed up in the opposite direction.

[swansont]

Mod note: Moved to classical physics from relativity

[nec209]

The rocket exhaust gases and these makes the rocket go up.If there was no hole for the exhaust gases the rocket would not take off .

 

The hole allows the exhaust gases and these makes the rocket go up.

 

The Newton law is any object that is moving has kinetic energy .What is kinetic energy it is energy of motion .Any object that is moving has kinetic energy .

 

The measure of its energy is its momentum.To eleberate in more detail momentum is mass and speed.The more massive the object is or the greater its speed , the geater it its momentum.A big car that is moving fast has alot of momentum and when it hits some thing it tries to keep moving

 

Any object that is not moving will not move unless a force makes it move and any object moving will not stop unless a force makes it stop or slow down.