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A 300 kg rocket sits on a launch pad. What is the thrust nee

  1. Mar 12, 2016 #1
    1. The problem statement, all variables and given/known data
    A 300 kg rocket sits on a launch pad. What is the thrust needed to obtain a thrust to weight ratio 3:1?

    2. Relevant equations

    3. The attempt at a solution
    300.0 kg x 9.817 m/s2 = 2945.1 N

    i know this is not the correct answer, but i have no idea where to start. can someone please help?
     
  2. jcsd
  3. Mar 12, 2016 #2

    BvU

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    Hello JD,
    what do you think they mean with a thrust to weight ratio ?
     
  4. Mar 12, 2016 #3
    the amount of acceleration it needs in order to thrust an object with the mass of 300 kg?
     
  5. Mar 12, 2016 #4
    I do not have much experience with this sort of equation but I believe that the equation for thrust to weight ratio is T/W where T is the force of the thrust and W is the weight of the given body measured in newtons hope this helps
     
  6. Mar 12, 2016 #5
    so based on your equation, would it be 3 / 2945.1 N? that would equal 0.00101864113. what would the units be?
     
  7. Mar 12, 2016 #6
    I think you would have to find the force of thrust so that T/W would be equivalent to 3/1
     
  8. Mar 12, 2016 #7
    how do i do that?
     
  9. Mar 12, 2016 #8

    SteamKing

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    Do you know what a ratio is?

    Here's an example:

    The ratio of centimeters to meters is 100 to 1.

    You are asked to find the thrust such that a thrust to weight ratio of 3 to 1 is obtained. You have already determined the weight of the rocket.
     
  10. Mar 12, 2016 #9
    do i multiply 2945.1 by 3? i'm not quite sure how to find the thrust.
     
  11. Mar 12, 2016 #10

    SteamKing

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    weight = mass × acceleration due to gravity

    You calculated the weight of the rocket in Post #1 (2945.1 N)

    You want the thrust o this rocket to be 3 times its weight.

    Therefore, the thrust = ?
     
  12. Mar 12, 2016 #11
    thrust = 2945.1 N x 3 = 8835.3 N?
     
  13. Mar 12, 2016 #12
    I believe that that is correct

    If this is the case then excellent job
     
  14. Mar 12, 2016 #13

    SteamKing

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    That looks OK.
     
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