Writing Center
Fall 2005 Edition

Physics, Adaptation, Evolution

Joshua Pettit
Expository 2010 2nd Place

The motor bike that I was riding weighs close to four hundred pounds, and street bikes with street tires do not have a lot of traction on dirt trails. The bike is fast and has a lot of torque. I was on a dirt road and had just been challenged to a race by a couple of guys who were riding 2001 Banshees. A Banshee is a two-stroke four-wheeler with more than an ample amount of power. The race was about 15 miles long as the crow flies. Could I win? My bike reaches maximum acceleration at 130 miles an hour. A Banshee reaches maximum acceleration at about ninety MPH (unless modified). In the back of my mind, I was thinking, “Is this a test of skill, and knowledge of physics, or just plain stupid?”

As a person who contemplates the forces of nature on a daily basis, I have come to understand the laws of physics quite well. I believe that understanding physics makes me a better motorbike rider and vehicle operator in general. I am led to believe through my observations that all living beings, from microorganisms to manatees, use physics unconsciously in their everyday lives. And evolution would be impossible if the ability to contemplate, at some level of consciousness, the physics of an environment were not a part of every living organism’s genetic code.

Because street tires have very little traction on the dirt, I would have to go very slowly on some of the turns unless I could figure a way to position my bike so that I could use the power of the engine to get more traction. This would be a very dangerous maneuver. If I had the bike pointed in the wrong direction by just a couple of degrees, I would go off the road when I dropped the clutch and gave it full throttle. The back tire could also slide out from underneath the bike if I did not have the bike straight up and down. This would be a test of skill vs. speed and traction. I was betting that with my knowledge of physics, I could calculate the speed and angles that I would need to hit the corners with the fastest speeds possible.

I already knew that I could make this bike fly, so the jumps on the way were no real challenge. The first half of the race was full of short straight-aways and U-shaped corners. I was behind the Banshees until the first long stretch of road opened up. I pulled back on the throttle and cycled through the gears. I had enough time to get to fourth gear, which is about 110 MPH, and then to use my engine to slow me back down. I got to sixty MPH, hit a cattle guard, and jumped my bike about fifty feet; right when I slammed back onto the ground, I realized there was a ninety degree corner directly in front of me. I stepped on the back brake and leaned my bike into a skid. As soon as the tire broke free and started sliding, I used the gas to help straighten the bike into the direction that I wanted to go. I gave the bike full throttle and leaned forward to keep the front end down; at the same time, I used my feet to push on the pegs, an action which directed more force onto the back tire for extra traction. I executed the maneuver perfectly and only had to slow down to 35 MPH. The guy behind me was not so lucky; he ran into my back tire and knocked me over.

I always used to imagine what I would do if I had to lay my bike on its side so that I would not lose my leg. I always thought that I would jump off the pegs, land on the side of my bike, and “surf” it until it stopped, and that is exactly what I did. As soon as I  was on the side of my bike, I saw him fly over me and land in a river bed. He could have avoided all this had he known of Newton’s first law of motion, which states that an object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction, unless acted upon by an opposing force.

The guy on the Banshee did not realize that he should have taken the corner wider to give himself more time to apply the brake and engine, which are the opposing forces. Once the tire breaks free of the ground and starts to slide, there is less resistance to the bike. The bike will slide in the same direction whether or not you turn the wheel. This is the reason I had my bike pointed in the direction I wanted to go and gave a lot of spinning power to the back wheel:  It provided an opposite force, which allowed the bike to go toward the desired direction. I proved that knowing some simple physics could save my life when I was faced with a dangerous situation.

Humans use physics every day, and most do not even know it. Every time we drive a car, we try to keep a certain distance behind a car because we are taught that it does take time to slow down a heavy object when it is traveling at a certain velocity. Subconsciously, people understand Newton’s second law of motion. The law states that the acceleration of an object is dependent upon two variables--the net-force acting upon the object and the mass of the object.  People understand that if something big is moving fast toward them, it is going to hurt if it hits them.

The better a person is at observing and applying the laws of physics consciously, rather than unconsciously, the more control he/she will have at operating a vehicle in the manner needed at the right time to avoid serious accidents. For example, when I am driving, I am always aware of every side of the vehicle.  I am constantly applying three second rule they taught us in Drivers’ Ed. I look in my rearview mirror and know exactly how far the person is behind me. I know that if I have to stop fast, the guy behind me will seriously injure or kill me because he is too close.

A couple of years ago, I had to stop at a red light on Bluff Street in St. George, Utah. The speed limit there is 45 miles an hour, but I know that at about 700 South, the average speed that everybody really goes is about 55 - 60 mph. I looked in my rearview mirror and saw the guy behind me was in a late 70's Ford LTD (a pile of steel) coming right at me; the guy obviously had no idea the light was red. I knew he was doing at least the speed limit and was already to close to stop without hitting me. I knew that no one was coming in the cross traffic so I applied full power to the engine and sped across the street. The guy had enough time to realize that my tires were spinning and slam on the brake. I knew that the force of his car hitting me while I was moving in the same direction would be less than if he hit me when standing still. I also knew that it would give him more time to react on the brake, which would lessen the impact force even more. This one of many times I escaped death by knowing how to “soften” the blow. His car missed my back bumper by a foot at the most. Fortunately, nobody was hurt.

I have a friend who lives in Southern Utah. He was riding a bullet bike at 140 MPH on the freeway and came up behind a semi truck; he waited until he was about ten feet from the back then tried to go around it. The wind that was generated from the displacement of air, caused by the truck, rippled out just like water. The guy had no idea this would happen. His speed, times the density of the air that was displaced from the truck, and multiplied by their velocities, equaled a force opposite his direction and a very negative reaction. The Bernoulli Effect states that the pressure is lower in a moving fluid/gas than in a stationary fluid/gas. The force of wind created in the instant he came around the truck lifted the bike straight into the air. He tried to hold onto the handle bar and inadvertently gave the bike more throttle, which spun the bike backward even more and threw him onto his back. He slid on his back for the length of three football fields.
After three hours of material extraction surgery, he picked gravel rocks out of his back for two years. Had he ever been told about the Bernoulli Effect, he would have understood such a stunt is a lose/lose situation.

The most practical example of the Bernoulli Effect is in the action of an airfoil. The shape of an airplane wing is such that air flowing over the top of the wing must travel faster than the air flowing under the wing so there is less pressure on the top than on the bottom, resulting in lift. An Indianapolis 500 race car uses a wing to displace the lift of the front by using the wind that goes across the top to force the car down. Someone who is racing motor cross or jumping motor bikes needs to know how fast and in what direction the wind is blowing because when in the air the bike has less resistance and is blown off course.

Not only humans, but every living animal applies physics unconsciously, every day in their natural life. Lions and other animals of prey calculate their prey’s speed and trajectory of their turns in a run to gain a tactical advantage. One day I was sitting on a cliff that overlooks the southern mountains of Kolob Canyon in Southern Utah. I started dreaming that I was a bird that could disappear high into the sky, roll over to warm my belly by the sun,  point my nose to the ground, tuck my wings back, and, at the right moment, swoosh right across the top of the grass and in and out of the trees. Just then I looked down and found a hawk feather; I started to think about birds. Birds are constantly in tune with the thermodynamics of air. Their brains use natural phenomena related to physics and electromagnetism. They have a sensor in them that tells them when the earth has experienced an electromagnetic storm from the sun that will cause great winds. They can also sense the direction north electromagnetically (Johnson). This is how they know when and how early they must leave to fly south for the winter and what direction south is.

Do birds sit around and contemplate the dynamics of wind? Do they understand what the Bernoulli Effect is? Not the word, but the meaning. Do they think when soaring towards a mouse at 150 miles per hour that they need to adjust their wings at a certain moment, or do they just do it? Do they ever think “What would happen if I held out until...” or “What can I do differently?”

Evolution is the closest word that I can find that explains the need to understand physics. When an organism experiences extreme conditions, it analyzes the physical conditions of its surroundings and adapts to the situation. If the organism cannot adapt, it will die. Humans have genetic traits that have evolved due to their environments; for example, on the islands of Southeast Asia, the children have started to adapt to seeing under water, because they swim underwater to catch their food, and have done so for generations (Science News). Human genes are influenced by many factors, including factors in the environment (Berger). The eye has to figure out how to see clearly in its given environment and has made a genetic trait, stored this trait in the chromosomes, and improved that trait throughout generations of use. In areas of the world where raising cattle has for generations been unknown or unpracticed, people are more likely to be lactose intolerant. However, people who come from cattle farming communities and who have been drinking milk for a couple hundred years have developed an enzyme that breaks down the lactose. For us to evolve off this rock, we need to understand the physics of earth, space, and quite possibly the physical effects created from a multi-dimensional universe. Understanding the physics involved in our daily lives is the first step into the vast oceans of answers, endless question, and wonder.

Works Cited:

Johnson, Sonke, and Lhomann, Kenneth J. “Magnetoreception, the Neurobiology of.”
2004. Duke University. 16 Sept.2005.

National Wildlife Foundation.
< http://www.nwf.org/migratorybirds/ >.

Travis J. “Children of Sea See Clearly Under Water-Gypsy Secret-Nomadic Sea Gypsies.” Science News 17 May 2003. 16 Sep. 2005

Berger, Kathleen S. The Developing Person: Though The Life Span. Vol. 6. New York:
Worth Publishers, 2005.