I Had a Car Crash
by Roadrunner – September 11, 2007
Additional comments on Newton’s Third Law by Dr. Morgan Reynolds. (excerpt from June 20, 2007 article)
Figure 1. Silhouette of passage by invincible Boeing 767?
Figure 2. Silhouette of passage by Invincible Roadrunner. Hmmmmmm!?
Figure 3. Meep! Meep!
I Had a Car Crash by Roadrunner (September 11, 2007)
Yesterday, I was driving from Tucson to Saguaro National Park in my big ol’ Toyota Landcruiser. It was a perfect day — no Wile E. Coyote and not a cloud in the sky. Unfortunately, I was involved in a collision with a big Dump Truck.
I was going about 50 mph as I came over a hill and saw this big truck in my way. It was too late to steer around it. But I knew what to do! Using what I’d learned about physics on 9/11-forums recently, I knew if I hit my brakes I would still be going 25 mph at impact. My SUV would be wiped out in the collision with the huge truck, so instead I put the pedal to the metal and I must have been going 150 mph by the time I hit it. My quick thinking saved me. The stationary truck could not stand up to the massive kinetic energy of my Toyota. I sliced through that big truck and left a neat hole the exact shape of my Landcruiser (just like I always do). It was really cool how my Toyota and I remained perfectly intact.
Just before the front of my SUV came out from the other end of the Dump Truck, I realized that any moment my car would suddenly shred into nothing â€“ and me with it. Just in the nick of time, I flung open the door and jumped out.
I thought my SUV completely disappeared, but they found the steering wheel 500 feet away and apparently one of the headrests flew over Mount Lemmon (el. 9,157 ft.) and landed on top of a saguaro cactus where the sherriff photographed it.
I am eternally indebted to Arabesque, reprehensor, and Greg Jenkins for saving my life because it was their words which I remembered in that split second when I had to decide whether to brake or accelerate. The speed of my impact with that huge Dump Truck made a huge difference. If I had hit my brakes, my car and I would have been wiped out.
P.S. I really appreciate the person from ACME Steel Airplane Company who found my passport and turned it in. It was on the back seat when I went through the Dump Truck and of course it ended up near the Dump Truck after my Landcruiser disappeared.
P.P.S. I am also thankful that I was driving a Toyota Landcruiser. Deputy Reynolds told me that if I had been in a hulking Ford Expedition, I would not be here today. But, thank God, Landcruisers behave differently in a crash situation.
Figure 4. Speeding 2003 Toyota Landcruiser ended up under this truck.
Figure 5. I survived WTC2 falling on me.
About Newton’s Third Law by Morgan Reynolds, Ph.D.
What follows is an excerpt from June 20, 2007 article.
We might understand Roadrunner’s confusion by considering Newton’s third law explicitly. According to Newton, whenever objects A and B interact with each other, they exert forces upon each other. A force may be defined here as a push or pull upon an object which results from its interaction with another object. Newton stated his third law of motion exactly as:
“To every action there is always opposed an equal reaction: or, the mutual actions of two bodies upon each other are always equal, and directed to contrary parts.”
To restate it, “For every action, there is an equal (in size) and opposite (in direction) reaction.”
To nail this concept down, consider classroom example 1:
Q: An unfortunate bug strikes the windshield of a bus moving down the road. Quite obviously, this is a case of Newton’s third law of motion. The bug hit the windshield and the windshield hit the bug. Which of the two forces is greater: the force on the bug or the force on the bus windshield?
A: Each force is the same size. For every action, there is an equal … (equal!). The fact that the bug splatters only means that with its smaller mass and strength, it is less able to withstand the force resulting from the interaction.
Now consider example 2:
Q: A speeding plane strikes the wall of a (“motionless”) Tower. Obviously this contact between objects is a case of Newton’s third law of motion. An aluminum plane hits the steel building and the building hits the plane. Which of the two forces is greater: the force on the plane or the force on the building?
A: Each force is the same size. For every action, there is an equal and opposite reaction. The fact that the steel beams, spandrel belts, and steel-reinforced concrete floors of 5-6 stories shatter, fragment and form an airplane-shaped gash…OOPS…you’re kidding! This correction just in: the fact that an aluminum plane crumples, shatters and leaves no “airplane-shaped silhouette of passage” in a collision against massive quantities of structural steel only means that with its lower mass, density and strength relative to the building, the plane is far less able to withstand the equal force exerted on both bodies.
We can check our understanding with a few calculations. Each WTC Tower weighed approximately 500,000 tons. As a first approximation, if a plane hit the upper five floors, these floors would weigh approximately 22,727 tons (5 floors divided by 110 floors = 4.5 percent of 500,000 tons). A Boeing 767 would weigh approximately 140 tons flying as described by government and media. The mass of such a plane would be 0.6 percent of the mass of five floors in a Tower (140/22,757). Therefore, the aluminum plane would be less than one percent of the mass of the section of the steel/concrete building it allegedly hit. The plane’s material density and strength (resistance to forces like bending, etc.) would also be vastly inferior to those of a Tower.
Conclusion: bye-bye airplane.
Critics may object that the steel beams in upper stories were thinner than those in lower floors (less building mass to support with nothing else lighter on upper stories), so generously shrink the estimated weight of the upper five stories by one-third, yielding 15,152 tons. The mass of a 767 would be 0.9 percent of the mass of five floors it theoretically hit. To restate it: the mass of the building section allegedly hit by the hollow aluminum tube with engines and wings and no crash rating is 100 times that of the plane.
Result: bye-bye airplane.
And what if the mass of the plane were even smaller?
Same answer: bye-bye airplane.
What if a plane flew faster into the steel tower? Impact force increases but remains equal for plane and tower at any speed. The tower is immensely stronger and harder than the plane.
Upshot: bye-bye airplane.
Figure 6.Three-pound bird goes mano a mano with aluminum plane and does heavy damage.
Figure 7.Airliner damage by bird impacts.
In real life, Building 100, Aluminum Tin Can 3 (maybe).
Morgan, keep pushing for the touchdown.