| MadSci Network: Physics |
You were a little bit short on details, so I am going to have to give a general answer. i think at the next recess you can try these out and see what was causing you to slide faster.
Whenever you slide there are two major forces in action - gravity and friction.
On a level surface gravity only pulls you straight down. It does not pull you forward. When a surface is tilted, gravity will both pull you down and forward. That is why you have to lean back to stop from falling.
Friction is the resistance to sliding. If you try to push your hand across the slide you will notice that it is hard to do so. If you were to spray some oil to the slide there will be less resistance or less friction, and it will be easier to slide your hand on the slide. Physicists can measure the resistance or force opposing the movement of your hand. They can also measure the amount of force pushing against the surface (the slide in this case). The ratio of the two is called the coefficient of friction. The lower the number, the easier you slide. Lubricants such as oil have low coefficients of friction. Nonslip treads for stairs have a high coefficient of friction.
Skin had a pretty high coefficient of friction. If you look carefully at your hands for example you can see little ridges on your fingertips that help you grab things and are what cause fingerprints. Even smooth skin like what is found on your legs tends to not slide easily. That is part of the reason you normally do not fall out of a chair when you move or turn. On the other hand, fabric has a much lower coefficient of friction. That means that it offers less resistance to sliding.
If when you were sitting up while sliding your bare legs were rubbing against the slide, you would tend to go slow because your legs offer a large amount of resistance to sliding. If you lifted up your legs, you would tend to go faster because only fabric (your pants) is touching the slide and there is less friction. If you slide lying down with no skin touching the slide you would also go fast because the friction is low with just the fabric touching the slide. [note added by MadSci Admin: Any rubber or plastic labels on the pants could also affect the friction!]
Another possibility is the heels your shoes were rubbing against the slide. Since most people do not like to slip and fall, most shoes have soles with high coefficients of friction. Just like bare skin they would slow you down as you tried to slide.
I hope this answers your question. At least you should now be able to go out and do some experiments on the slide to answer your question better.
Try the links in the MadSci Library for more information on Physics.