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Homework Help: Force provided during deceleration?

  1. Nov 2, 2015 #1
    1. The problem statement, all variables and given/known data
    A spacecraft with a mass of 9100kg (incl fuel) travelling 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?

    2. Relevant equations
    acceleration = ∆v/t
    F = m x a

    3. 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
  2. jcsd
  3. Nov 2, 2015 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

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