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!

How to find velocity of air at certain point if car is moving at certain speed (Fluid Mechanics)?

  1. Nov 13, 2014 #1
    1. The problem statement, all variables and given/known data

    The shape of a car windshield is approximated in the figure below; its length is 2.0 ft and height is 1.5 ft. Obtain an equation of the windshield shape r as a function of
    θ,
    r(θ), in the polar coordinate system shown in the picture.

    When the car moves at 55 mph, determine the velocity of the air at points A and B.

    28b87iq.jpg

    2. Relevant equations

    Not really sure how to approach this...maybe Bernoulli's Equation? We've been studying the method of repeating variables, but I'm unsure how I would apply that. I really don't know where to begin with this one!

    3. The attempt at a solution

    (P/rho + v^2/2 + gz = constant)
    But I don't know the pressure difference...I'm hopelessly stuck :( If anyone could help shed some light on this, and just give me an idea where to even begin, that would be very appreciated!
     
  2. jcsd
  3. Nov 14, 2014 #2
    This seems to be a trick question. Have you heard of the "no slip" boundary condition?

    Chet
     
  4. Nov 14, 2014 #3
    Ah, so v_A = 0.
     
  5. Nov 14, 2014 #4
    Relative to the car. Relative to the ground, it's U = 55 mph.

    Chet
     
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: How to find velocity of air at certain point if car is moving at certain speed (Fluid Mechanics)?
Loading...