Sidewalk Ice Dancing

We all know how slippery the sidewalks are in the winter. Falling on icy surfaces are "same-level" falls and two types of slips usually occur. One type of slip is where the heel of the forward foot contacts the walking surface, the front foot slips forward and the person falls backward. Another type of slip is when the rear foot slips backwards, the forward force is on the sole of the rear foot and as the rear heel is lifted the force moves to the front of the sole and the person falls.

Traction is the force that allows us to walk without slipping and traction is measured as the "coefficient of friction (COF)." To prevent slips and falls a high COF is needed between shoes and the walking surface. Shoes with soft rubber soles and heels with rubber cleats provide a high COF (0.40-0.50). On very slippery surfaces, falling down may be unavoidable, especially when you're in a rush, and no type of footwear may provide a safe COF.

On a positive note, think of all the cool new dance moves that are created when people have close calls. For instance, there's the Jazz Hands, the Disco Man, the Bear Crawl, the Pretty Princess, the Matrix Man, and the MJ. Maybe you have some of your own moves to add to the list.

Source: University of Florida IFAS Extension

Distracted Walking

Bob, distracted by a big exam he was about to take, walked out of his residence hall on a mission to make it to class on time. He wanted to get an A on this test. He was listening to his iPod to pump himself up. A friend texted him "good luck." While texting back he failed to notice the ice patch on the sidewalk ahead of him. He hit the ice and his feet flew out in front of him. Not only did he fall, he slid into a group of people and knocked them over.

Why is ice slippery? There's a lot of science behind walking on a warm sunny day, but add some winter into the mix and we have some difficulties. Ice is the solid state of water. Many solids retain their shape, but with ice it's not quite like that. The top layer isn't "packed in" like the rest of the layers, so it can move a bit. This is called a quasi-liquid layer and this thin layer of water causes us to slip. Slips and falls on low-friction surfaces cause many injuries a year and tribologists continue to study sliding surfaces and the role of friction.

What could Bob have done to prevent a fall?

1. Paid closer attention to his surroundings.
2. Taken smaller steps to maintain his balance when he encountered the ice patch.
3. Chosen appropriate footwear for the weather conditions.

Sources:
www.purdue.edu/newsroom/research/2009/091207KneppSnowflake.html
www.newscientist.com/article/mg20427392.000

Solar Roads

Winter driving. The white knuckle slide, the scraping sound underneath the car, and the glorious dry pavement. I've often wondered if roads could be imbedded with solar devices to warm the pavement of ice and snow. While this video doesn't answer that question, it does explore an interesting alternative energy concept.

Solar Roadways Video

I can remember 9 years ago when I went to see the movie "Snow Day". This movie is about a group of kids who try to hijack the snowplow on a snow day in order to keep the school closed for longer. These kids pull ridiculous pranks on the snowplow driver. While it's an amusing movie, I feel almost sorry for the poor snowplow driver.

In real life these drivers work night and day to keep the roads safe and clear. They have to work around vehicles, water hydrants and many other things. While this is a service we all appreciate, I will admit I have been really upset by a plow burying my car in snow. We can all do things to help us be prepared for snow and snowplows. Make sure you have an ice scraper and brush in your house. That way you won't have to get into your car before it's cleaned off to get your scraper. Park in your designated spot, outside your house, building, etc., or in a garage if you have one. Something that is not very smart to do is to leave your car in a large parking lot, such as outside a store. It will get buried. Let's appreciate what the snowplow drivers do for us and make their jobs easier.


Blog: A day in the life of a snowplow operator