April Streff

Labor 2

Dr. Richard Barrans

October 17, 2011

Suddenly it happens—you are in an old elevator with no safety backup system when the cable snaps, and the elevator cab falls. What should you do to optimize your chance of survival, as slim as that might be? For example, should you jump up just before the cab collides with the bottom of the shaft?

Newton’s third law states, for every action there is an equal and opposite reaction. This is where impulse comes in, Impulse=force/time. Impulse matters because if the amont of time of impact is increased than the force is decreased. Less force means less damage to the person. When the elevator reaches the ground on the fast impact, the speed and force that the elevator cab is free falling with will be put upon the cab after the impact. The impulse affects the elevator cab and whatever is in the elevator cab. The momentum of the earth is so much greater than the person that when they collide the person feels a huge change in momentum whereas the earth is virtually unaffected because it is so massive.

If the person was to stay standing on their two feet the force is applied only to the surface of their feet. The feet and ankles will take on all the force and pressure causing potential serious injuries. There is also a myth about jumping just before the elevator hits the bottom. Even if the person could time the impact perfectly to jump at the exact time it still would not help because the elevator is likely to ricochet off the ground after impact. By jumping in the air the person is coming back down as the elevator is going up. Since the person is traveling the opposite direction of the elevator they feel the full rebound force of the elevator. When the person meets the elevator floor after the jump the force will be even stronger than if the person were to stay on the ground the elevator hitting the bottom.

If the person lays flat on the floor of the elevator there will be more surface area of the body to absorb the impact so the pressure will be less. Pressure is force per unit area, P=F/T. According to that equation the larger the area the force is applied to the less the pressure on the receiving object. So if the elevator cables do break and the cab starts crashing to the ground the passengers should lay flat on the floor of the cab. Although it will still be extremely painful the entire body is taking the impact instead of one single part of your body will be taking the brunt of the crash.

Although the laws of physics say lying down flat on the floor, either on the front or back is your best bet there are still complications that go with that. If you do lay down your soft tissues, organs and brain, are absorbing the impact, which could cause damages. You should cushion your head if possible but that is not always proven to work.

Annotated Bibliography

Kurtus, Ron. "School for Champions'." Force. N.p., n.d. Web. 26 Oct 2011. . This reference is talks about force and what exactly force is. It explains all about pressure and how that is tied to force. I used it for the formula pressure equals force divided by area. I had to understand the reasoning behind laying down in the elevator rather than standing up, according to this reference laying down works because the force of the impact will be less because it is being applied to a larger surface area. I trusted this source because the authors name was directly at the top. It was very obvious he was proud of his work, the information is well organized, the text is supported by diagrams and there are ads on the side of the page which means it is well known and advertisers trust it

"What if you were on an elevator and the cable broke." How stuff works, A discovery company . A discovery Company , n.d. Web. 26 Oct 2011. . This reference really explained the engineering behind elevators and how they work. It discusses how extremely unlikely it is for an elevator to crash to the ground because all of the safety features in the modern elevator. Then it explains what to do if the unlikely event does happen. It tells what to do and why, and explains why the myth of jumping would not work. I used this source for my own understanding of how often and why it is unlikely for elevators to crash. Then I used the suggestions of what to do and what not to do to further my investigation into the question. I trusted this website because it seemed to know the entire engineering behind elevators. I did have some prior knowledge and that was discussed and then furthered. This source, like the first, had sponsoring ads on the sides which sold to me that is was reliable.

Gerbis, Nicholas. "How to survive an elevator free fall." Lifes little Mysteries . N.p., 12 August 2011. Web. 26 Oct 2011. . This journal discussed in detail what to do if the elevator falls. It adds humor to the potential scary situation. It also mentions different situations where the outcome could change. I used it as a follow up to the previous reference because it does go into depth of what the elevator rider should do. I used it for the bulk of my research. This is a trusted source because it comes from a well known journal called Life’s little Mysteries. This had been published so the reader can actually get a hard copy of it.