# Rocket thrust force calculation

robax25

## Homework Statement

A rocket has weight 10,000 kg and it needs to carry 5000 kg with acceleration 3.5 m/s². How much thrust force is necessary for the rocket to have a flight from Earth to space?

F=ma[/B]

## The Attempt at a Solution

I try that, According to Newton's law, ( g=10 m/s2) ΣF=ma Ft=15000 kg * 10 m/s² - 15000 kg * 3.5m/s² =97500N.
[/B]

Hey may I know why did you subtract the force of rocket on Earth and force of 5 ton object accelerated at 3.5m/s2

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robax25
you will get resultant force

Then 3.5m/2 is the acceleration of the rocket, is that right?

robax25
yeah but then the equation,
F= (15000)*3.5=52500N

I gave it a try.. check that out..

robax25
why you add two acceleration? one is upward direction and another one is negative direction? My first solution is valid for space

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you will get resultant force
The resultant force is theforce that leads to its actual acceleration. The two applied forces must be added to get the resultant force.
What are the two applied forces, and what is the resultant force?

robax25
resultant force=thrust force- weight of the rocket, we do not add two forces and I need to subtract them because they are negative direction each other,
= 202500 N- 150000N
= 52500N