Force provided during deceleration?

[TommyChestnut]

Homework Statement

A spacecraft with a mass of 9100kg (incl fuel) traveling at 8 m/s
Rockets fire for 10 seconds burning 100kg of fuel slowing the spacecraft to 0.03 m/s
What is the force the rockets provided during the 10 seconds?

Homework Equations

acceleration = ∆v/t
F = m x a[/B]

The Attempt at a Solution

a = 8m/s - 0.03m/s = 7.97m/s
F = 9100kg x 7.97ms / 10s
F = 7.252.7

I just wanted to check the equations I have used for this problem are correct as I am getting confused with changes in momentum F x t = m x v[/B]

 

[SteamKing]

Homework Statement

A spacecraft with a mass of 9100kg (incl fuel) traveling at 8 m/s
Rockets fire for 10 seconds burning 100kg of fuel slowing the spacecraft to 0.03 m/s
What is the force the rockets provided during the 10 seconds?

Homework Equations

acceleration = ∆v/t
F = m x a[/B]

The Attempt at a Solution

a = 8m/s - 0.03m/s = 7.97m/s
F = 9100kg x 7.97ms / 10s
F = 7.252.7

I just wanted to check the equations I have used for this problem are correct as I am getting confused with changes in momentum F x t = m x v[/B]

You have a variable mass situation here, since you are burning fuel to slow the spacecraft .