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Homework Help: How do I Calculate Average Thrust when given t, v, delta m

  1. Oct 17, 2016 #1
    1. The problem statement, all variables and given/known data
    During a .0050 second time period a rocket expels 1.000kg of gas at a velocity of 5000 m/s. Calculate the rockets average Thrust, as well as Impulse. http://imgur.com/a/uE9dV

    I am going to use this note for reference on a test and want to rock solid about it.

    2. Relevant equations

    I have the formulas given by my professor are

    Thrust= v exhaust * (delta mass / time)

    Impulse rocket= v exhasut (delta mass)= delta p rocket
    3. The attempt at a solution

    Like I said I want to be sure of this so I can refer to it later. Here is my best try

    Thrust= (5000m/s)*(1.000kg/.0050s) = 5000 m/s * 200 kg/s= 10000000 kg m/s

    Impulse= 5000 m/s (1.000 kg) = 5000kg m/s

    So please tell me if and where I have gone wrong.
    Last edited by a moderator: Oct 17, 2016
  2. jcsd
  3. Oct 17, 2016 #2
    Looks good from where I'm at.
  4. Oct 17, 2016 #3
    Thanks for your response. I am in the process of doing the same with Coefficient of Restitution, speed of approach over speed of separation. Thanks again
  5. Oct 17, 2016 #4


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    Science Advisor
    Homework Helper
    Gold Member

    Check the number of zeroes.
    The way the information is stated makes me suspect they are also looking for the right precision being expressed in the answer. It might be better to write it as 1.000 (or whatever is the right precision) times a power of ten.
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