When the Publisher (Houghton Mifflin Harcourt) sent me Randall Munroe's (of xkcd comic) book to review, I was excited. I pointed out to my 12 year old son that he might like this book too. The next day, I was looking for the book and it was missing. Yup, my son had it. I think he read through the whole thing in just one long car trip and a couple of other sessions.
Well, if he read it before me I might as well get a mini-book review from him.
A 12 Year Old's Review ———————-
Me: So, what did you learn from reading this book?
12 yo: I learned that if you put some of the elements in the periodic table next to each other, they will explode.
Me: What was your favorite part?
12 yo: I liked the periodic table one. I liked the "could everyone jump" part. Did you know that the book mentions your blog in that one? I also liked the other questions that he didn't answer. Those were funny.
So overall, he liked the book. I think that really says something about the writing and content in the book. It's interesting, but simple enough that a 12 year old could understand it. Oh sure, he didn't understand everything, but he still liked it.
What If? vs. Dot Physics ————————
Actually, What If? is a lot like my blog. We both try to find answers to sometimes silly questions. Also we both use physics concepts and even try to explain some of the physics. However, there are a couple of big differences.
Randall tends to actually research some topics before getting answer. I, on the other hand, usually avoid looking for similar problems that have been done. I like to start from scratch and build my own model.
I tend to show more of the steps when solving a problem. Maybe this isn't the best way to write a blog post, but it's what I do. I like to include all the details so that readers can see the thought process that goes into solving these types of problems. In the end, I think Randall's style of condensing the solution down to the most basic parts makes for a more readable solution.
A few comments on the book. —————————
I like to point out errors. In one part of the book Randall answers the question: could you ride your bike so fast in the winter that the compression of the air would warm you up? Randall says the following: the fastest bike is 40 m/s. If you went 200 m/s, this could work. Since air resistance is proportional to velocity squared, this would require an increase in power by a factor of 25. This is wrong. Here is a picture.
In this case, you could say that the work done to ride the bike is from the frictional force. Suppose the bike moves a distance s. Since this frictional force must be equal to the air resistance (for constant velocity), the work done in this case would be:
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But what about the power? Power would be the work divided by the time it takes to move. So, I can write:
So, the power is proportional to the velocity cubed, not squared. Increasing the speed by a factor of 5 would increase the power by a factor of 125.
Of course Randall's point is still valid. You can't ride a bike at 200 m/s.
Ok, how about another comment. In one chapter, Randall looks at the power Yoda would need to lift an x-wing fighter. This answer was awesome, but it makes me just a little sad when I read it. I guess a better word would be "jealous". I'm jealous that Randall thought of this interesting problem before I did. It's a great question with an awesome answer.
Like I said, there are many interesting questions with entertaining answers. I enjoyed the book
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