1. 2010

    Velocity addition: a myth?

    On the episode of Mythbusters aired a couple weeks back, Kari, Grant, and Tory set out to test the myth that if you have a car driving forward at, say, 60 miles per hour, and you shoot a ball out the back at the same speed, it will fall straight down. Now, if you know anything about physics, your first thought upon hearing this might have been the same as mine: “huwhah?” The idea that velocities of equal magnitude and opposite direction cancel each other out in this way is a pretty fundamental result…

  2. 2009

    Dirty vs. Clean Car

    Hot on the heels of their Bullet Fired vs. Bullet Dropped episode, the Mythbusters have another result that’s poised to shake up the world of science… well, maybe not. But this week’s main myth, Dirty vs. Clean Car, is the kind of neat idea that most of us would never think to test and yet turns out to be surprisingly close to practicality. The myth that Adam and Jamie are testing is that dirt on a car has the same kind of effect as golf ball dimples, increasing the fuel efficiency of the car. To sum up the results (SPOILER ALERT ;-), it doesn’t work, at least not with dirt — but putting an actual dimpled coating on a car does increase the fuel efficiency by 11%. (Only on Mythbusters would they dimple a car…)

    As with a lot of recent myths, this one deals with fluid dynamics — but not just the simple stuff like drag force, as in the bullet myths. The golf ball effect is based on turbulence, specifically the idea that the rough surface of the ball induces turbulence which disrupts the wake (pocket of still air) that trails behind the ball. That pocket of still …