Why Do Pirates Love Parrots? (25 page)
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Authors: David Feldman
T
elephone poles don’t
always
extend far above the highest wire,” Bill Sherrard, a spokesperson for Long Island Lighting assured us, although conceding that they often do. Corporate librarian Julie Swift of Michigan Bell, a division of Ameritech, backs him up:
In the case of telephone poles, poles with only phone lines on them extend only about a foot above the cable to provide room for future expansion.
So when you’re seeing a pole much higher than the telephone wires, chances are the telephone company is sharing a pole with the electric utility and, possibly, a cable operator. According to Swift, for these shared poles, “It is the electric company that determines for their own reasons how much pole to leave above the cables.” Usually, the highest-voltage wires are put on top, so the order from the bottom up, is telephone, cable, and electrical wires. Of course, whoever built the pole receives rent from the other companies sharing the pole. As cable providers have inched into the telephony domain of what were once monopolies, some telephone companies have fought back by trying to drastically raise their rates.
Although the main purpose of the “extra” height of the pole is to provide for expansion, there are at least two other benefits provided. The tops of most poles are grounded so that if they are hit by lightning, the charge will hit the ground wire rather than disabling a working circuit lower down. And the excess pole gives birds an alternative to crosspieces as a place to perch. The danger isn’t from electrocution by perching on copper wires. The wires are well insulated, and even if they weren’t, a body is a lousy conductor compared to a wire—no current would flow through the bird. But when a big bird spreads its wings and accidentally touches two energized parts or one energized wire and a grounded metal part, the result is one sizzled bird.
Submitted by Allen Jamieson of Sacramento, California.
A
t first, we didn’t want to answer this Imponderable. For some reason, this is a favorite question among listeners on call-in radio shows, but we wondered whether many people really ponder over this conundrum. When a caller on a radio show recently sounded downright desperate for an answer, we decided to do something about her plight.
We filled up the official Imponderables Central bathtub with water and proceeded to gently place a can of Diet Coke and a can of Classic Coke, both twelve-ouncers, into the tub. Indeed, the Coke dropped like the proverbial stone, while the Diet Coke floated lugubriously on the surface.
As is our wont when we are faced with a daunting physics challenge, we sidled up to our consulting physicist, John DiBartolo, of Polytechnic University (who will henceforth be identified as J.D.) and demanded an explanation:
IMPS:
What’s the deal?
J.D.:
The upward force on a submerged can is the buoyant force, and it depends on the can’s volume (its size). The downward force is gravity, or in other words, the can’s mass (its weight). (Mass is a property closely related to weight. Although technically not the same, for the purpose of this discussion we can use these terms interchangeably.)
If Diet Coke floats while Coke sinks, it means at least one of the following:
1) A can of Diet Coke is larger than a can of Coke
2) A can of Diet Coke weighs less than a can of Coke
I’m not sure which of these is true.
So, we contacted our pals at Coca-Cola and were told that the cans used for both drinks are identical. We were not the first people to pose this question to the soft drink behemoth, and we were provided with this answer from the industry and consumer affairs department:
Sugar-sweetened products are sweetened with high fructose corn syrup (HFCS) and/or sucrose, both of which are types of sugar. Most of our diet products are sweetened with aspartame and/or a combination of aspartame and acesulfame potassium, both of which are low-calorie sweeteners.
Because aspartame is sweeter than sugar, it takes less aspartame than sugar to make a product taste [just as sweet]. Therefore, the density of Coca-Cola Classic is approximately 1.25 grams/milliliter, while the density of Diet Coke is 1.00 grams/milliliter. Based on these specifications, it would be correct to assume that the diet products would float in water, while sugar-sweetened products would sink.
Coca-Cola’s statement soft-pedals the difference in the amount of sweeteners in each. There are approximately 39 grams of sugar in a twelve-ounce can of Coke, and only about 200 milligrams (one-fifth of a gram) of Nutrasweet (the trade name for aspartame) in Diet Coke. That’s right—there is 195 times the amount of sugar (by weight) in Coca-Cola Classic as Nutrasweet in Diet Coke. So now we ran back to Mr. Physicist:
IMPS:
The labels say there are 12 fluid ounces and 355 milliliters in each can. Do they mean the same thing?
J.D.:
Yup. You know that 355 milliliters refers to fluid volume because a “milliliter” is a unit of fluid volume. A “fluid ounce” is simply another unit of fluid volume. (One fluid ounce is 29.6 milliliters).
The volume of something is a measure of the amount of space it takes up. 355 milliliters of water and 355 milliliters of mercury both take up the same amount of space.
IMPS:
If there is more sugar in Coke than Nutrasweet in Diet Coke, does that mean there is less unsweetened liquid in Coke than Diet Coke? Does that mean Coke weighs more than Diet Coke?
J.D.:
Since the complete recipe for each beverage has to fit in 12 fluid ounces of volume, then more sweetener means less space for presweetened liquid. Since sugar and Nutrasweet are each denser than the presweetened liquid, any space taken from the presweetened liquid and given to the sweetener will increase the overall weight of the sweetened beverage. (Actually, a certain mass of a sweetener takes up less space when dissolved in a liquid than it does when in its solid form. That means that it does a particularly good job at increasing the mass of the sweetened beverage while taking up very little space.)
This means that the same volume of Coke (which has much more sweetener in it) weighs more than the same volume of Diet Coke. In other words, Coke is more dense than Diet Coke.
IMPS:
OK, so Coke is denser than Diet-Coke. Why does that make Coke sink?
J.D.:
The heavier an object is, the greater the downward pull on the object. The bigger the object is, the greater the upward pull on the object. When an object is denser than water, the downward pull is greater than the upward pull, and the object sinks. When an object is less dense than water, the upward pull is greater than the downward pull, and the object floats.
IMPS:
So if you have two identical cans, does it matter what’s inside as far as “sinkability” goes? Will a 12-ounce can of Coke sink and a can of marbles that weigh less float? Does it matter what kind of liquid is in the can? Whether it’s carbonated or not? Or is weight (its mass) all that matters?
J.D.:
The only thing that affects whether the can floats or sinks is the weight of its contents. This is because the only two determining factors for buoyancy are can size (unaffected by its contents) and can weight (affected only by the weight of its contents).
Therefore a can will behave exactly the same way if it contains Coke, marbles, or tiny marshmallows, provided the weight of each of these is the same.
IMPS
: Prove it, physics boy!
J.D.:
OK, Imponderable dude. I weighed six different cans of Coke as well as six different cans of Diet Coke. I then emptied the cans and repeated the measurements. For each six-pack, I subtracted the average empty can weight from the average full can weight, which gives the average weight of the fluid inside the can. Here are the results (together with the error due to instrument precision and statistical variation):
Mass of fluid in can of Coke: 370.5 grams (
±
0.8 grams).
Mass of fluid in can of Diet Coke: 353.8 grams (
±
1.3 grams).
Based on these measurements, it appears that the contents in a can of Coke weigh about 17 grams more than the contents in a can of Diet Coke.
IMPS:
And yet they don’t charge more for the Coke!
J.D.:
Shhh, we’re conducting an important experiment here. Now that I showed that Coke weighs more than Diet Coke, the next question is: Is this true because there’s more fluid in the Coke can than in the Diet Coke can? To answer this, I measured the volume of the liquid in each can. As it turns out, when Coca-Cola says there are twelve fluid ounces (355 milliliters) of soda in each can, they’re not kidding.
My measurements showed that for both Coke and Diet Coke, the average volume of the fluid inside was indeed 355 milliliters (
±
0.5 milliliters). Because the volumes are equal for both drinks, this tells us that the discrepancy in weight is due to the fact that Coke is more dense than Diet Coke (where density is found by dividing mass by volume). Speaking of densities, here are the results:
Density of Coke: 1.044 grams/milliliter (
±
.004 grams/milliliter).
Density of Diet Coke: 0.997 grams/milliliter (
±
.005 grams/milliliter).
As we guessed earlier from the large difference between masses of sweeteners added to each drink, there is a difference in drink densities. (The density of Coke quoted by Coca-Cola seems to be way off, by the way.) Well, whaddya know? This physics thing actually works sometimes.
Is the Nobel Committee watching? The 2005 winners in physics won for “…contribution to the quantum theory of optical coherence” and “the development of laser-based precision spectroscopy, including the optical frequency comb technique.” We think DiBartolo’s Coke–Diet Coke research is more important.
Truth be told, we figured out the density part of the equation, but it didn’t occur to us that in a sense the density issue is a red herring: The greater amount of solids (i.e., sugar) makes the Coke denser than Diet Coke; the greater density of the Coke makes the full cans of Coke heavier than the Diet Coke; but ultimately it is only its higher weight that sinks the Classic Coke.
Submitted by Jay Ballinger, of parts unknown. Thanks also to Craig Blanchard of Seattle, Washington; and Shana Grey, via the Internet.
