The answer to this question can only be said with opinion, but I can tell you that the Landyachtz Evo has won more consecutive downhill racing championships than any other longboard in the world. It's a drop-through board with a drop down design. It was designed by DH riders specifically for going downhill. This would be your best bet, if you'd like to go crazy fast. If you're just a casual longboarder, then there are hundreds of different longboards meant for downhill.
uphill, for an experiment look for "Do forest fires move faster uphill or down hill
The answer to your question is in the questiong itself.
you bend down, don't turn, keep skis straight, and you do better the more weight you have
because if you going down hill its faster because its a mountain
A snowball. When rolling downhill, a snowball accumulates more snow and gathers momentum, making it faster than when it's rolling uphill.
Gravity is the force that makes the car move faster down the slope. As the car descends, gravity pulls it downhill, increasing its speed. The steeper the slope, the greater the acceleration due to gravity.
skateboarding with a longboard, not a trick board, and carving/bombing down hills
Unless you have some additional force such as from a bike or car, you cannot get faster than terminal velocity.This is because of the extra forces acting to slow you down besides air pressure.
As water runs downhill, it gains kinetic energy and flows faster. It may also erode the soil and rocks it passes over, creating channels and gullies. The water may collect in larger bodies such as rivers or lakes as it continues its journey downhill.
the chap with a spanner down his pants
i don't know if this is a trick question or not.up hill because a bear can't run downhill because it's front lega are shorter than the back ones so it would be more likely to roll downhill