## How does a Rocket moves in the space?

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seonguvai
Posts: 1
Joined: Thu Apr 02, 2015 4:49 am

### How does a Rocket moves in the space?

How does a rocket moves in the space? By newton's third law of physics a force must be used to boost the rocket. In the earth it can be easily done because the rocket;s fuel use force to move on. But in the space there's no air or gas or anything.

So by this law, how does a rocket moves in the space?

Catria
Posts: 354
Joined: Fri Oct 26, 2012 4:14 pm

### Re: How does a Rocket moves in the space?

seonguvai wrote:How does a rocket moves in the space? By newton's third law of physics a force must be used to boost the rocket. In the earth it can be easily done because the rocket;s fuel use force to move on. But in the space there's no air or gas or anything.

So by this law, how does a rocket moves in the space?
A rocket engine has to expel mass in some way; it uses conservation of momentum to do so. The rocket law,

$$\Delta V = V_e \log\left( \frac{M_i}{M_f}\right)$$

says that, given the ejection speed of the fuel, the initial and final mass of the rocket, you can get the difference of velocities between launch and the time where you know the rocket's mass.

deterministic devil
Posts: 21
Joined: Mon Nov 17, 2014 7:22 am

### Re: How does a Rocket moves in the space?

seonguvai wrote:How does a rocket moves in the space? By newton's third law of physics a force must be used to boost the rocket. In the earth it can be easily done because the rocket;s fuel use force to move on. But in the space there's no air or gas or anything.

So by this law, how does a rocket moves in the space?
In the space it uses less fuel to produce the same amount of thrust since there is no air molecules (close to vacuum) causing the drag force (friction).