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I just saw a great clip on the fastest skateboarder to date. He wants to reach 160 mph from a dropped board, but says his speed is limited by the roads currently available. What is the shortest run required for a "dropped skateboard" rider to reach 160 mph? Is it even possible?

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No, his speed is limited by air resistance. Straight down he'll hit 120 mph. – Ignacio Vazquez-Abrams Aug 1 '12 at 2:42
If he's skating in a vacuum, will he reach 160 mph before he asphyxiates? Feel free to assume a spherical skateboarder. – Keith Thompson Aug 1 '12 at 2:50
That should be a uniform, spherical skateboarder to keep things as simple as possible... – dmckee♦ Aug 1 '12 at 3:14
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@IgnacioVazquez-Abrams - 120mph is for a spread-eagled skydiver. A head down, arms back long boarder pose might do 160mph – Martin Beckett Aug 1 '12 at 3:40
@Martin: At that point you're not skateboarding. – Ignacio Vazquez-Abrams Aug 1 '12 at 3:43
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As posted above the general value for terminal velocity is around 120mph. But this is for skydivers in a stable arms spreadeagle pose. Speed skiers on steep hills with streamlined clothing reach 156mph (251km/h).

Presumably if you had low enough rolling friction, a long and smooth enough road (and sufficient levels of stupid) you could do this on wheels

If you can ignore mechanical friction then the speed limit only depends on aerodynamics, ie only on your shape (assuming air at standard temperature and pressure) so with enough time you could achieve this on a hill of any slope. A steeper slope merely gives you more power to reduce the effect of rolling friction in the wheels.

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