I notice that the answers are posted for the “Presidential Physics quiz” in the NY Times (original quiz wording) and, well, blech. Sorta. I’ve read decent things about the Physics for Future Presidents book, but I don’t want this to be the example for “how to quiz presidents and justify the answers.”
QUESTION 1. How does the amount of energy per gram of TNT compare with the energy per gram of a chocolate chip cookie?
My answer is (d), the cookie contains nearly 10 times as much energy.
But the answer is really around 5 or 6, depending on what numbers you’ve used, and one of the other choices is “about the same.” If you’re going to do multiple-choice, try not to bracket the right answer this way.
I do like the defense of discounting the E=mc2 answer, because it shows recognition that we’re dealing with chemical rather than nuclear reactions. But in the defense of the answer, there’s
TNT explodes all by itself, no air needed.
Well, no, not really. If you balance the reaction, you’ll find that significant oxygen is needed. Sugars have oxygen in them, too. You still need external oxygen for that reaction as well.
But all of this ignores that science isn’t just a bunch of facts. What I’d rather see from a president (or student) is some reasoning, like “these are both basically combustion reactions, so to first order, I’d expect them to release similar amounts of energy” and worry about the details later on, like what difference there is because you have some nitrogen in TNT, and how that might affect the bottom line, and maybe the reasoning that you give up some energy for the convenience of a reaction that forms more moles of gases (and those gases want to occupy 22.4L each at STP, so boom!) instead of keeping the molar amount of gas the same (swapping CO2 for O2).
QUESTION 2. Based on the answer to the previous question, suggest an energy-efficient way to destroy a car.
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