How does a Rocket moves in the space?

  • This has become our largest and most active forum because the physics GRE is just one aspect of getting accepted into a graduate physics program.
  • There are applications, personal statements, letters of recommendation, visiting schools, anxiety of waiting for acceptances, deciding between schools, finding out where others are going, etc.

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

How does a Rocket moves in the space?

Postby seonguvai » Thu Apr 02, 2015 5:04 am

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: 353
Joined: Fri Oct 26, 2012 4:14 pm

Re: How does a Rocket moves in the space?

Postby Catria » Thu Apr 02, 2015 9:04 am

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?

Postby deterministic devil » Sun Apr 05, 2015 3:24 am

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).




Return to “Prospective Physics Graduate Student Topics”

Who is online

Users browsing this forum: No registered users and 3 guests