Sliding with Science

Created by Kate Bergum and Allison Luoma

Have you ever went down a water slide and wondered how you were sliding?
noahs ark in wisconsin dells
noahs ark in wisconsin dells
Question: What forces of motion are involved when sliding down a water slide?

Though the video clip above made water sliding look easy, several science related components were what made it happen. Potential Energy, friction, air resistance, gravity, Newton's Third and First Laws of Motion, accelaration, velocity, and inertia all have crucial roles in sliding down water slides.

Potential energy is equal to mass x accelaration due to gravity x height. Climbing the stairs of a steep water slide builds potential energy. The higher you go, the more potential energy you have. At the very top, you have reached your maximum potential energy. This is converted to kinetic energy, or the energy of moving things once you begin going down the slide.
Another component of sliding is friction. Friction is a force that opposes, or resists motion between objects moving, or trying to move past each other. On water slides, friction is the force that causes you to stick to the slide. When going down a slide, you want to go fast, so you don't want to stick to the slide very much. Because of this, water slides are designed to reduce friction. This is why water is run in a constant stream down a slide: it serves as a lubricant, which reduces friction. This is why you are able to slide down a water slide smoothly and quickly, without stopping.

Did you notice the position of the boy on the water slide? His arms were against his chest and his legs were crossed. This is because of air resistance.

Air resistance
is another type of friction involved with watersliding. Air resitance is the friction between the air and an object moving through it--in this case, the person sliding. If your body is more aerodynamic when going down a slide, you will go down faster, because your body can slip through the air far more easily. For this reason, on many steep water slides, people are asked to cross their arms and legs, like the boy in the video clip above. This position cuts through the air easier than one with spread arms and legs would. Thus, you go down the slide faster.

The slope of the slide also affects how quickly you go down it. When going down a slide, gravity pulls you down to the bottom of the slide. Opposing this force is the force of the slide, pushing you upward. This deals with Newton's Third Law of Gravity, which states that forces have pairs equal and opposite to them. Gravity's equal and opposite pair is the force that pushes objects upward. If a slide was horizontal, gravity would pull you down, and the slide would push you straight up. When the slant of the slide is very steep, the slide cannot push you straight up, it must push you up at a different angle. Because of this, the force resisting gravity is not as strong. This causes you to go faster down the slide.
This also partially explains how you stop when sliding down waterslides. When the angle becomes flatter, the force resisting gravity pushes you straight upward. The opposing force, which is gravity, must be opposite to the slide pushing up on you, so it pushes straight down on your body, instead of down the slide. Friction also increases, which makes you stop. This stopping is summarized by Newton's First Law of Gravity, which states that objects in motion will stay in motion unless acted upon by outside forces, and objects at rest will stay at rest unless acted upon by outside forces. When sliding, the object in motion, (you) keeps moving until outside forces (friction and the force of gravity pulling down on your body) make it come to a complete stop.
twisty slides = curved sides
twisty slides = curved sides

When you go down a slide with curves, your accelaration changes. This is because accelaration is the rate that velocity, which is speed going in a given direction, changes over time. When you go on a twist or turn, your direction changes, which causes your velocity to change as well. This causes you to accelarate, which can give slides that exciting feeling.
Curved slides also make gravity work against your intertia. Inertia is the property of matter that resists changes in motion. When on a water slide that has turns, your body wants to keep going straight because of inertia. This is why twisty slides need curved edges, or a tube like shape. Without them, your body would keep resisting the curve, resulting in you possibly being thrown from the slide.

water sliding = science!!
water sliding = science!!

Sources: (for more information on the physics of waterslides, check out these great sites!) noahs-ark-in-wiscon...

"Air and Air Resistance." Newton Ask a Scientist. United States Department of Energy, 13 Jul 2004. Web. 4 Apr 2010. <

"awesome water slide drop." youtube. Web. 3 Apr 2010

Harris, Tom. "How Water Slides Work." How Stuff Works. Discovery, n.d. Web. 23 March 2010. <>.

"Physics of Water Sliding." University of South Carolina at Chapel Hill, n.d. Web. 30 March 2010.

"the point of no return." youtube. Web. 3 Apr 2010.

"Wisconsin Dell's water slides." Web. 30 March 2010