June 6th, 2008 ecoli
Here’s a question posed by the Scientific Indian regarding bicycle balance. Given my new found love for bike riding (see breaking out the bike) I figured I’d give this one a go.
Here’s the question:
Which is easy: To maintain your balance when cycling uphill, or when cycling downhill? Assume you maintain a constant speed of 6 km/hr and the inclination is constant. If you like to challenge your proficiency in physics, assume further that you are negotiating a bend.
Here’s my answer (feel free to add your own). In terms of balance, it doesn’t make a difference, assuming a constant speed. However, due to a property of physics called torque, the speed it takes to travel uphill and downhill is rarely going to be the same, and that’s due to gravity.
Torque is what causes rotation in the wheels of the bike when you pedal, and is analogous to an angular force. Pushing the pedals creates torque. The pedals are a lever that turns the main cog, which pulls the chain, which cause rotation of the gear, which is attached to the wheel.
Most bicycles today consist of a gear shift that changes the gear ratio depending upon the speed. Different combinations of gears creates a different effect, by controlling the relative size of the front and rear cogs. A high gear ratio should be used on a flat surface, turns the wheel multiple times for each turn of the pedal. When traveling uphill, a lower gear ratio should be used, which results in having to pedal a lot to get the wheel to turn once.
However, what I’ve noticed from my own experience, is that the gears, when traveling uphill, will shift only when the bicyclist starts pedaling faster. If the biker tries to maintain the same pedal speed, the force of gravity will slow you down dramatically, you won’t have enough torque to keep the wheels moving at the same speed, momentum is lost and you lose balance. You have to pedal a lot harder and faster against gravity, so that the gear will shift to maintain speed.
The advantage to this, is that when you’re traveling on a flat surface, it would get tiring to have to pedal 5 times just to turn the wheel once (for example). But, when you’re going uphill, with gravity slowing you down, pedalling faster will help you keep momentum, and prevent falling over. If you tried to bike uphill on a high gear ratio, I suspect, your wheels would try to turn faster and travel than gravity allow, and you would slip backwards or simply tip over.
When traveling downhill, however, you have gravity on your side. The acceleration due to gravity maintaings your speed, without having to put much force into pedalling. Travelling fast, momentum is maintained, sometimes without having to pedal at all, depending on the steepness of the hill. A low gear ratio is maintained simply by virtue of the acceleration due to gravity.
The second part of your question is a simple matter of centripetal motion. When negotiating around a bend (which is just really traveling a fraction of a circular path, there’s some interesting physics at work.
At any given moment, the direction of the velocity will be straight ahead, but the force and acceleration will be pointing along the radius of the circle, towards the center. So, while turning, the body wants to move along the path of the velocity, and you’ll wind up leaning that way, making maintaining balance a little trickier.
Another interesting affect about turning while on a bicycle is called “counter-steering.” If you were to travel along a straight path and simply turn the wheel to the right, you’d simply fall over. This is because the center of mass must be under the bicycle in order to remain upright. Turning the wheel moves the center of mass out from under the bike. In order to successfully turn, you must first lean steer the bike slightly in the opposite direction of the turn in order to shift the center of mass to the correct position so you can later lean for the turn. It’s the same principle as balancing any object on your hand. You have to move the bottom of the object to the direction that the top of the object is falling, in order to reposition the center of mass. While this lean slight turn in the opposite direction is necessary for all speeds, it’s more noticable at high speeds, which is why decreasing velocity for a tighter turn in a good idea. But, if you decrease the speed too much, momentum will be lost (to friction) and the bike and rider will fall over. (thanks to Felstatsu for the correction)
I hope this answered The Scientific Indian’s question, and I hope all the physics is right. Please post any further questions or [hopefully no] errors.
Posted in musings, physics | 6 Comments »
June 6th, 2008 ecoli
I’m bringing in my laptop to get fixed today, after I finish backing up my important files. I can’t wait around anymore waiting for my damaged hard drive to fix itself. I hope Best Buy’s warranty covers this one, because this is one thing I have no desire to pay for.
I’m not sure how long they’ll have it for, but going by my other experiences with Best Buy’s Geek squad, it will be on the order of weeks. I’m not sure what my computer/net access will be like during that time.
Posted in musings | 1 Comment »
June 5th, 2008 ecoli
This graph from the NY times, kindly provided by Jake Young, at Pure Pedantry provides a good case for letting the market just do it’s thing, when it comes to alternative energies in regards to transportation.
If you’re an environmentalist, or if you don’t work for big oil, high gas prices is a good thing. When costs are artificially low, there’s little incentive for companies to produce alternative energies or hybrids. But, these charts show that inflated prices do, in fact, bring down the rate of fuel consumption (less driving). Now, corporations can only continue to inflate prices so much, before people start opting out of personal automobile use altogether, travel overseas by steamboat and start biking to work. In order for energy companies to keep selling energies, they’ll have to develop alternative sources.
Oil subsidies, paid for out of our taxes, keeps oil prices artifically low and less responsive to the laws of demand. This is harmful to our economy by preventing the development of alternative energies and harmful to our environment in the same respect.
If the gas tax is repealed for the summer, it will have a similiar effect by making gas prices appear cheaper, increasing demand and delying alternative technologies. The gas tax is needed to keep our public roadways in shape. Hillary’s proposal to add a windfall tax to oil companies and then fine companies millions who jack up prices to compensate for the loss is, at best, ridiculous. You can’t fine companies for trying to maintain their profits, and this would never be approved by a Bush appointed FTC administration anyway. Hillary’s plan would screw federal highways, because there’s no altervative source of income for this tax. And, it would delay the production of badly needed alternative energy by messing with the laws of demand. Leave the free market alone!
Posted in environment, link out, musings, politics | No Comments »
June 3rd, 2008 ecoli
Pure Pedantry cites this interesting article, showing that access to restaurants is statistically unrelated to the obesity epidemic.
The whole experiment can pretty much be summed up in these two graphs:
Though it has been suggested in the past, that eating at restaurant promotes a larger calorie intake, this study seems to show that this is unrelated to obesity at large.
Its interesting work, but I think there are too many assumptions that we are expected to take at their word. For example, what type of restaurants are these? Perhaps people who live near the restaurants are mostly eating at a health food vegan sandwhich place, while the other group is eating fast food.
The other issue, is that they assume that living near a restaurant indicates a higher likelyhood of eating out. While, it takes no imaginative leap to assume that, I think a study which claims statistical relavence needs to prove these sort of assumptions. For example, could we also not assume, that people who live near restaurants are sick and tired of seeing them all the time, and therefore would rather eat at home?
Posted in link out, musings | No Comments »
June 1st, 2008 ecoli
I’m sure I’m not the only who has noticed:
Google has changed it’s favicon, the icon that appears on the left hand side of the URL in most web browsers . They’ve moved away from their traditional upper case, classic “G”, to a lowercase “g.” Are they going for a sleeker look? Does this mark some bigger change in google?
We can only speculate, but I think they made the switch because Google is no longer just a company name, but a word that has become synonymous with the (now with a properly lowercase “i”) internet. “To google” has entered the ranks of English dictionaries, at least some online ones, as meaning:
to search for information on the Internet, esp. using the Google search engine
Google isn’t just a company anymore. It ‘belongs’ to the people, the internet-using public.
More on the story at the Google Blogoscope.
Posted in link out, musings, news | 8 Comments »
May 29th, 2008 ecoli
As if we didn’t have to worry about with just a robot revolution, now the animals and robots will be teaming up against us. Now, all we need is to throw some zombies in the mixed, and we’re screwed for sure.
Posted in musings | No Comments »
May 28th, 2008 ecoli
Orac at respectful insolence writes
If there’s one thing that quacks and cranks share in common, it’s that they do not like scrutiny, particularly by people with some scientific knowledge. Indeed, when confronted with scientists or educated lay people who can challenge their crankery, it’s amazing how they react the same way almost every time; they try to silence or–if you will–expel the person who challenges their world view. That’s because they want to control their message and operate within the confines of their cozy world, where never is heard a discouraging–and especially never critical–word. Most of all, they never, ever want their true agenda to see the light of day.
It’s about the the vaccination-autism people, but applies equally to creationists, 9/11 truthers and holocaust denialists just as readily.
Posted in link out, musings | 1 Comment »
May 27th, 2008 ecoli
Tim, at CAD Comics news (great comic, by the way) writes about the new Dungeons and Dragons system that’s coming out, known as D&D 4.0.
I, myself, am still playing (when I get the chance) D&D 3.0 having refused to take part in the debacle/ marketing scam that was D&D 3.5. I use my own house rules to cover the week points in the system and therefore bypass the need to give another 60+ dollars to Wizards of the Coast.
As a primarily pc/console gaming site, Tim says:
A few times I tried to get into the whole DnD roleplaying thing the best I could with both Neverwinter Nights 1 and 2, but it never really stuck, and I know it wouldn’t have been like real DnD anyway.
Hopefully someday they’ll successfully translate the DnD experience to something that can be played online.
I guess, and it seems odd to think this is true, Tim has never heard of the MMORPG that WotC released some time ago; D&D Online: Stormreach. I played that one for a while, being one of the only MMOs I’ve gotten into (that and Runescape). It’s a slightly inferior game than World of Warcraft, but its more genetically related to D&D, which I like better than WoW. The races, weapons and magic systems are more familiar to me, as a D&D player. I would much like to read to review of that game by Tim.
And one more thing:
In the meantime, the closest I get is my miniature wargaming, with Warmachine, which I absolutely love.
I never got into Warmachine, but I played Warhammer 40k for a while. I could spend any more money on table top wargaming systems; the models were getting too expensive. Plus, they kept changing the rules and mini designs. I still have all my models though. I can’t bring myself to part with them.
Well that’s all on that matter for now. I’m going to get back to that episode of Doctor Who that I was watching.
Posted in entertainment, musings | No Comments »
May 26th, 2008 ecoli
Pure Pedantry
Respectful Insolence
I haven’t seen it yet, but these reviews give a pretty good idea about the overall quality of the movie, without giving away anything important. Also, it reinforces the notion that I can rely on science blogs for the vast majority of my news, political or entertainment.
Posted in entertainment, link out, musings | No Comments »
May 26th, 2008 ecoli
I’ve been sitting on this one for a while now, wondering on how best to approach it.
For our anniversary, my girlfriend got me this box of 12 #2 Antimicrobial Pencils from Ticonderoga.
My first thought was, “WTF is wrong with the world” quickly followed by a “Why would you get this for me?” to my girlfriend. She shrugged and said “you like bacteria.”
Well, I guess I like them so much that she thought I should contribute to the growing problem of bacterial resistance to commercial antibiotics by introducing a new source of a completely useless product.
According to the front of the box:
Microban protection inhibits the growth of odor and stain causing bacteria
and according to Wikipedia:
Microban International, Ltd. produces chemicals used for antimicrobial product protection. These persistent chemicals provide antimicrobial properties in consumer, industrial and medical products… The broad application of the Microban product in everything from cutting boards to flooring, along with its long life in the product and hence the environment, has raised some concerns about the long term effects of its promiscuous use.
This could be a made up statistic, but 48.5 out of 50 microbiologists agree that the concept of Microban products is one of the stupidest they’ve heard in a while.
We’re overusing antimicrobial agents in everything from flooring, pencils and our colons. It’s no wonder that widespread antibiotic resistance is wreaking havoc in the medical field. Haven’t we seen in the recent spread of drug resistant superbugs, like MRSA)shown us the dangers of overusing antibiotics?
Apparantly not, because companies like Microban will not be satisfied until their antimicrobial products are in the lining of every pot and in the flooring of every garage. Just looking at that insidious green packaging, in it’s environmentally friendly guise, is making me angry.
I can see the attractiveness of wanting to put antibiotics into pencils, sort of. I suppose if you happen to be an elementary school teacher who’s students slobber all over their pencils, it could help stop the spread of germs,if they happen to share their pencils. But, this still, is going too far.
Bacteria will quickly build up resistance to these types of antibiotics, which is dangerous because of the increased virulence associated with increased resistance. So, instead of a few relatively harmless bacteria on your pencil, you’ve got lots of harmful bacteria.
This simple fact speaks to a larger ignorance in the general public about the simple fact that antimicrobial products become less effective when they’re overused. As a result, the doctor’s treatment arsenal is getting smaller, and science simply cannot produce new antibiotic agents as quickly as they are needed.
I am going to send an email to Microban International, Ltd to give them a piece of my mind, and I urge all my readers to do the same. Perhaps we can pressure them into at least recognizing the potential problem associated with their company.
(my email - feel free to use this version or modify as needed for your own letters)
I am writing as a student in microbiology and biochemistry to express my concern about the general content and implications of your Microban products.
As you may or may not know, antimicrobial products are important tool in medicine and treating infectious diseases, however, their overuse is leading to a serious health problem.
This company, which seeks to put antimicrobial products into everything from flooring to pencils, is doing the public a great disservice. It is important to realize that not all bacteria or fungi are killed by antimicrobials, and that the pathogens that survive are often the strongest and most virulent of the population. These organisms are also largely resistant to antimicrobials.
Therefore, as more antimicrobials enter general use, they become less effective. This is annoying problem for those concerned with household odors. This is an potential public health catastrophe to those, like myself, who can envision what the overuse of antimicrobial products will bring.
In the news we see with cases like the MRSA superbug, which have been able to outmaneuver our antibiotics faster than science can produce them, and the result is often fatal (to children). This is one of hundreds of different cases of virulent diseases made worse by overuse of antibiotics.
I write to urge this company to reconsider the way it approaches and applies it’s products.
Right now, overuse of antimicrobials is a nuisance, but in the future it could become a real health epidemic if this overuse is continued. If Microban International, Ltd. truly cares about the public good and its consumer base, it will seriously reconsider its business approach.
Sincerely and respectfully,
Posted in business, education, environment, evolution, microbiology, musings | 3 Comments »
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