1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Rocket Question - 2 solutions?

  1. Jan 9, 2013 #1
    1. The problem statement, all variables and given/known data

    A rocket of initial total mass mi leaves a space station in deep space, far from all sources of gravitation. The rocket ejects burn fuel at a constant speed u << c relative to the rocket.

    (a) Derive an expression for the rocket relative to the space station when the total mass of the rocket plus remaining fuel is mf.


    (b) Some time after the rocket has left the space station, a small quantity of the ejected fuel remains stationary in the frame of the space station. What limit does this observation place upon the fraction of the original total mass that was burnt as fuel?

    (c) The rocket ejects fuel at a rate proportional to its remaining total mass m, so that (dm/dt) = -αm. Derive an expression for the distance x between the space station and the stationary burnt fuel. Obtain a value for x given that u = 1000 ms-1, and that m is reduced to half its starting value after 10 minutes.

    3. The attempt at a solution

    Part (a)

    2w4b1xe.png

    Part (b)

    2ludp5h.png

    Part (c)

    Method 1

    4udhdi.png

    Method 2

    34i5vyr.png
     
  2. jcsd
  3. Jan 9, 2013 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    In the second line in method 2, there is "m" missing in the denominator of the right side.
    And the units of the result do not match as a consequence.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Rocket Question - 2 solutions?
Loading...