1. 2013

    Drag under the Indy car

    As you might be able to tell by the lack of activity on the blog, I’ve been pretty busy the past couple weeks. Which makes it kind of hard to write about Mythbusters at my usual level of detail.

    Fortunately, Rhett Allain has already done it for me. He analyzed last week’s episode to figure out whether air pressure is enough to pick up a manhole cover. And it is: an air pressure of \(\SI{101325}{Pa}\), normal atmospheric pressure, applied to a manhole’s surface area of \(\SI{0.369}{m^2}\) (seriously, click the link), gives a force of \(\SI{37400}{N}\) — over eight thousand pounds! That’s way more than enough to pick up a 300-pound manhole cover.

    Of course, that would only happen if the manhole cover had a near-perfect vacuum above it. Perhaps if it were a manhole on a spaceship. But that’s not the situation on Mythbusters. (How cool would that be? Mythbusters in space… but I digress.) The manhole cover under an Indy car has air on both sides; the pressure of the air above is reduced, though, due to Bernoulli’s principle.

    $$P_1 + \frac{1}{2}\rho v_1^2 …