Re: How can surface texture change the speed of a skateboard?

Paul,

Trying to skate faster huh?  Well, I'm assuming you mean the surface 
texture of whatever you're riding on, and not of the skateboard.  I don't 
think changing the surface texture of the skateboard would have much 
effect on speed.

But, the texture of the surface you're riding on will definitely effect 
how fast you can go.  You've probably noticed that you can go faster on 
smooth surfaces like wood ramps, tile floors, smooth sidewalks.  But you 
get slowed down on rough streets and probably can't even move on gravel.  

The difference between all these surfaces is the friction.  Friction is a 
force that trys to stop motion between two things (like the ground and 
your skateboard).  Friction is affected by two things:  the surfaces in 
contact, and the amount of force (or weight) between them.  Rougher 
surfaces have more friction, and smooth surfaces have less.  Also, more 
weight means more friction (you can probably kick your skateboard and it 
will roll farther than it would if you were standing on it).  

Here's a simple experiment to demonstrate friction to you.  Take a sheet 
of paper and put it on your kitchen table.  Now just slide it around.  
Moves pretty easy, right?  That's because you have two smooth surfaces in 
contact; so the friction is pretty low.  Now, put a book on top of the 
paper.  It's harder to move now, right?  That's because there's more 
friction with more weight.  Now try the same experiment on the carpet, 
sidewalk, road, whatever.  The same things that make the paper harder to 
slide around, slow down your skateboard when you're riding along.  

Rough/bumpy surfaces create more friction, because there are more little 
nooks and crannies for the two surface to hook together and slow each 
other down.  You can image the rough surface tries to "dig in" to the 
paper (or your skateboard wheels) and tries to stop it.  

This also explains why different skateboard wheels will be faster or 
slower on different surfaces.  A hard wheel will go real fast on nice 
smooth surfaces.  A softer wheel will "grip" to the surface more and slow 
you down (you can notice the difference if you try to drag a hard wheel 
and a soft wheel across a smooth floor).  But, a hard wheel probably won't 
do too well on a really rough surface.  The hard wheel will get bounced 
around more, and a lot of your momentum (or your "energy") going forward 
will get used up by bouncing up and down.  But a soft wheel will deform a 
little bit and ride over the imperfections and go a little faster-and also 
give you a smoother ride.  

Hope that helps you out.  Have fun skating.

Your Mad Scientist,
Mike Scannell