# What is thrust?

What is thrust??

can someone please give me a brief explanation about the thrust force?

## Answers and Replies

Gold Member

In short, it is Newton's third law. If you expel mass from, say, a rocket nozzle, the exhaust has a certain momentum. The rocket feels a force that is equal and opposite this.

Cliff Hanley
jbriggs444
Homework Helper

Thrust is the forward force that impels you to go faster or to keep going in the intended direction. Thrust is usually desireable.

Drag is the backward force that slows you down. Drag is usually undesireable.

If you are talking aerodynamics then lift is the crosswise force that keeps you in the air. Lift is usually desireable.

You need thrust to offset drag so that you can have motion and lift.

sorry for the late reply and thanks for your answers

Bobbywhy
Gold Member

raw 653, Just book a commercial flight on a jetliner, and get yourself a window seat just behind the wing. This gives you a great view of the nozzles of the jet engines. You can imagine the "thrust" of the exhaust gasses during takeoff, for example. I promise you that you will understand (and feel) what is "thrust".

i`ll try to do that next time :)

how about calculating the Thrust force? how can you do it and what are the equations used?

Bobbywhy
Gold Member

Google is our friend, and Wiki is, well, an extremely important and valuable encyclopedia that you find using Google. You should become intimate (yes, intimate)with both of them. One caution: sometimes Wiki has mistaken/wrong information: use it with care and verify everything you read there.

This Wiki page has all the formulas for calculating the thrust force:

http://en.wikipedia.org/wiki/Thrust

Cheers,
Bobbywhy