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Homework Help: Thrust of a rocket at lift-off

  1. Jun 2, 2004 #1
    Need help with an ancient A lvl question. Just cant visualise the whole process even though I drew out the diagram

    A space research Rocket stands vertically on its launching-pad. Prior to ignition, gas is ejected from the rocker at a speed of 2.5x10^3 ms^-1 relative to the rocket, and fuel is consumed at a constand rate of 7.4kgs^-1. Find the thrust of the rocket and hence explain why there is an interval between ignition and lift-off

    g = 10ms-2

    I have totally no idea how to find the thrust. =(
  2. jcsd
  3. Jun 2, 2004 #2
    there's not much one can do with two numbers. Try some dimensional analysis to see if it fits.

    But regardless...you can already have an idea about the second question. Take a guess.
  4. Jun 2, 2004 #3
    BTW: a force is a change of momentum (the derivative)
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