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!

B Model Rocket- What does the 'v' in drag=kv^2 really mean?

  1. May 26, 2016 #1
    Hello! I am predicting the peak altitude of a model rocket based on some ground tests. I know that Total Force on the rocket=Thrust-mg-kv^2 but am stuck as to which value for 'v' to use? Is it the velocity of the rocket with the effects of gravity and air resistance taken into account or the velocity purely from the motor (without any air resistance or gravity taken into account)?

    Your help is appreciated, thanks.
     
  2. jcsd
  3. May 26, 2016 #2

    DrClaude

    User Avatar

    Staff: Mentor

    The velocity at any given time is the rate of change of position over time, how fast the object is actually going. There is no such thing as "the velocity purely from the motor": the motor does not give a velocity, it gives a force. The velocity will be the result of all the forces acting on the object (and its previous velocity if it is already moving).
     
  4. May 26, 2016 #3

    A.T.

    User Avatar
    Science Advisor
    Gold Member

  5. May 27, 2016 #4

    DrClaude

    User Avatar

    Staff: Mentor

  6. May 27, 2016 #5
    Thanks for your response.. I understand now. I actually calculated the velocity based on some ground testing (where I found out the impulse of the motor) and was hoping to incorporate drag.. This may give you context: https://www.physicsforums.com/threads/coefficient-of-drag-on-a-model-rocket.871810/
    Thanks for your help though, I think I might just leave incorporating drag into my calculations as I have 2 unknowns- the force due to drag as well as the actual velocity. Thanks again,
    Andrea
     
  7. May 27, 2016 #6
    In this context, the terms "drag" and "air resistance" are synonymous.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Model Rocket- What does the 'v' in drag=kv^2 really mean?
Loading...