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!

Drag Force and Terminal Speed

  1. Oct 28, 2009 #1
    1. The problem statement, all variables and given/known data
    Missile Calculate the drag force on a missile 48 cm in diameter cruising with a speed of 270 m/s at low altitude, where the density of air is 1.2 kg/m3. Assume C = 0.75.



    2. Relevant equations

    Fd = -1/2p(v^2)CA

    3. The attempt at a solution

    -1/2(1.2)(270^2)(0.75(0.48) = -15746.4 what am i doing wrong?
     
  2. jcsd
  3. Oct 28, 2009 #2
    0.48 is the diameter, not the cross-sectional area of the missile.
     
  4. Oct 28, 2009 #3
    how do i calculate cross-sectional area?
     
  5. Oct 28, 2009 #4
    Err...
    Well, the usage of the term 'diameter' and general impression of the appearance of the missile should clearly hint towards approximating it as a cylinder / having a round cross-section at least.
     
  6. Oct 28, 2009 #5

    ideasrule

    User Avatar
    Homework Helper

    The question mentions diameter, so you're supposed to assume the missile is a cylinder.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook