James Leong | Web Developer

Recently, I was talking with a cha bo and she told me how she was really impressed by a guy who talked to her about the coefficient of friction.

It was late in the night and the rain was barely over when this ham sub ta bo (HSTB) called this “intelligent” cha bo (”I”CG) and asked her out for a late night jog at botanical gardens.

HSTB: “No. this is the best time to jog, after the rain,”

“I”CG: “Oh really. Why? Because there is more water vapour in the air and we don’t have to stop too often to drink to replenish the water in our body?”

HSTB: “No. Because the pavement is moist, the coefficient of friction is higher and hence the traction is better.”

….

HSTB: “You know when the floor is slightly moist, the friction is better because the coefficient is changed. That is why the running tracks are sprayed with water, making them slightly moist, during the Olympics before the race.”

“I”CG: “Wow. Really? I didn’t know that. Wow!” (Very impressed)

Honestly, it just does not make sense to me. How can wet floors actually increase the coefficient of friction. We have been told since young to:

Be careful… the floor is wet and slippery

Yet… just by mentioning some stupid spraying of water on Olympic tracks and “I”CG is fully taken in by the fact that water does increase the coefficient of friction. Don’t we all know that cars tend to skid easily on wet roads (just look at the number of accidents on a wet day)… and that’s why we have to add grooves in the tyres. Theoretically, on a dry day, tyres without grooves have a higher coefficient of friction as a larger surface area of the rubber is in contact with the road (yes coefficient of friction depends on the size of the surface area in contact with the road).

However, during rainy days, if there were no grooves, the tyre’s rubber will not be in contact with the road. As such, tyres need grooves to allow water to drain through. Check out:

http://en.wikipedia.org/wiki/Rain_tyre (Show u article to prove that i not smoking)

It doesn’t take much effort to extend this concept to our shoes. Why are there grooves on the shoes or slippers? These grooves are there… simply to allow the water to drain through… so that the rubberised soles can be in contact with the ground. That’s why worn out slippers are very slippery when you walk around with it in the wet market.

If the floor is not wet, there will be need for such grooves… If a floor is wet, your soles better have the necessary grooves….. so how does having a wet floor increase the coefficient of friction in these instances?

BTW: I have tried to search the entire wikipedia and howstuffworks website… and have yet to come up with any article that talks about spraying the olympic tracks before running…. Not that I doubt the validity of the statement… for it does make sense. We all know rubber when clean tends to be more sticky. So the cleaning of the tracks in an effort to remove the dirt & soil particles should have some effect in increasing its grip. Also the tracks are actually sloping inwards towards lane 1… so that water will naturally drain off into a drain next to the 1st lane….. (the reason for doing so has little to do with coefficient of friction but more on the maintainability of stadium tracks as wet rubber is more vulnerable to wear and tear…)

But that only applies to rubberised tracks.

Do they have rubberised tracks in botanical garden?

The entire argument seems to hinge on a specific anomality, an instance of inconsistency, to the natural laws of our world. Its like saying that matter contracts when heated and expands when cooled and then support it by looking at water when it is at 4 degrees celsius. It like taking a particular verse out of the bible and intepreting it all on its own….. Just in case you do not get the idea, here are some examples:

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Ham Sub Boyfriend (HSB): Do you know things expand when they are cooled?

“Intelligent” Girlfriend (”I”G): Really? But I thought it was the other way round….

HSB: No, you look at the frozen pond. Dun you realise that there is ice on top and water at the bottom? The fact that there is ice on top shows that ice is less dense than water… and thus the water has expanded as it was cooled to become ice…

“I”CG: “Wow. Really? I didn’t know that. Wow!” (Very impressed)

“I”CG: “Hmmm… maybe we should make our bedroom a little colder the next time….”

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HSB: You know… we should really have a little sex once in a while.

“I”G: Really? But I thought it was bad…..

HSB: No…. did you not realise in Genesis 1:28, the bible actually tells us to… “Be fruitful and increase in number; fill the earth and subdue it……” Well, the earth is pretty big… so we better get started….

“I”CG: “Wow. Really? I didn’t know that. Wow!” (Very impressed)

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Man… this is the trashiest stuff I have ever written in my blog. Please ignore it. Maybe botanical garden has rubberised tracks…..

This entry was posted on Thursday, May 3rd, 2007 at 3:13 pm and is filed under Musings. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.