{"id":5103,"date":"2010-10-11T10:35:06","date_gmt":"2010-10-11T10:35:06","guid":{"rendered":"http:\/\/scienceblogs.com\/principles\/2010\/10\/11\/physics-is-not-a-mad-lib\/"},"modified":"2010-10-11T10:35:06","modified_gmt":"2010-10-11T10:35:06","slug":"physics-is-not-a-mad-lib","status":"publish","type":"post","link":"http:\/\/chadorzel.com\/principles\/2010\/10\/11\/physics-is-not-a-mad-lib\/","title":{"rendered":"Physics Is Not a Mad Lib"},"content":{"rendered":"

Via Tom<\/a>, a site giving problem-solving advice for physics<\/a>. While the general advice is good, and the friendly, Don’t-Panic tone is great, I do have a problem with one of their steps, Step 7: Consider Your Formulas:<\/p>\n

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Some professors will require that you memorize relevant formulas, while others will give you a “cheat sheet.” Either way, you have what you need. Memorization might sound horrible, but most physics subjects don’t have that many equations to memorize. I remember taking an advanced electromagnetism course where I had to memorize about 20 different formulas. At first it seemed terrible, and I kept remembering them wrong. However, the more you use the formulas, and the more you understand what they mean and – if you care enough to check – where they came from, the easier it gets to remember them.<\/p>\n

Organize your formulas in front of you. If you have a cheat sheet, align it next to your variables. What formula can you fill up, leaving the least amount of missing variables? Which formula can help you solve the question?<\/p>\n

See it? Use it.<\/p>\n<\/blockquote>\n

It’s not that this step is necessarily ineffective– for certain classes of physics problems, it’s actually a very sensible and efficient way to attack the problem. In fact, I used to give students a problem-solving spiel that was just a variant on this.<\/p>\n

Over time, though, I’ve started to think that while this advice is good early on, it sets students (and thus faculty) up for a major problem later on. And by later on, I don’t mean “in upper-level physics classes,” I mean “a few weeks later in the same class.”<\/p>\n

<\/p>\n

The “find the formula with all the relevant variables” method works best for kinematics problems, which is the first topic covered in most introductory mechanics classes, and thus the first physics topic most college students see. In kinematics problems involving one object, there are six numbers you can possibly know or care about (initial and final positions, initial and final velocity, acceleration, and time), and you can effectively attack almost any problem by making a table of these six values, and determining which you know and which you care about. This will almost always lead you to the right formula to use to solve the problem in the fastest way possible.<\/p>\n

The problem with this approach is that it sets students up to believe that physics is like a mad lib. You’ve got a bunch of possible formulas, and a bunch of variables that slot into those formulas, and it’s just a question of fitting the right things into the right places.<\/p>\n

This approach fails spectacularly about two weeks later, when you start doing problems about forces, for the simple reason that you no longer have a wide selection of possible formulas that you just select and plug numbers into. While the six-number table worked great for kinematics, I would constantly get students asking “Which formula do I use?” two weeks later. It’s a simple question to answer, because there’s only one: F=ma. That answer doesn’t really help students accustomed to the pick-a-formula method, though.<\/p>\n

While it’s still true that you can pick things that feed into F=ma based on what information you’re given– if it has a spring, then you use Hooke’s law, etc.– but ultimately, the only way to solve force problems is through understanding what’s going on: What forces act? In what directions? What do you know about the motion? You can eventually get the problem down to an expression that you can plug numbers into, but it requires a bunch of thought before you get there, and you have to know what you’re doing.<\/p>\n

So while the pick-a-formula method works for some things, it’s kind of a dangerous bit of advice. There’s really no substitute for understanding the physics of the situation, but the pick-a-formula method can make it seem like there is, and that sets students up for trouble later on.<\/p>\n

Of course, this leaves professors in a bit of a bind, because the pick-a-formula method is<\/em> effective for the early part, and even if you don’t tell students to do it that way, they’ll discover it for themselves. You can kind of get around it by phrasing the problems in ways that force students to do something else– the Matter and Interactions<\/a> curriculum we use now does some of this, by not giving the kinematic formulas that most pick-a-formula methods rely on, but insisting that students derive the results from simpler rules. This runs the risk of convincing students, particularly those who have had a good high school class where they saw the relevant formulas, that you’re just being a dick for no real reason, though.<\/p>\n

Anyway, this is a bit of a nit-pick regarding what is generally a solid page of advice for students. Particularly the part about not panicking. If you’re taking introductory physics, by all means, read this page carefully and think about what it’s telling you. But don’t rely too heavily on Step 7, because while it works some of the time, it will let you down in the end.<\/p>\n","protected":false},"excerpt":{"rendered":"

Via Tom, a site giving problem-solving advice for physics. While the general advice is good, and the friendly, Don’t-Panic tone is great, I do have a problem with one of their steps, Step 7: Consider Your Formulas: Some professors will require that you memorize relevant formulas, while others will give you a “cheat sheet.” Either… Continue reading Physics Is Not a Mad Lib<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"1","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8,13,7,11],"tags":[],"class_list":["post-5103","post","type-post","status-publish","format-standard","hentry","category-academia","category-education","category-physics","category-science","entry"],"_links":{"self":[{"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/posts\/5103","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/comments?post=5103"}],"version-history":[{"count":0,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/posts\/5103\/revisions"}],"wp:attachment":[{"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/media?parent=5103"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/categories?post=5103"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/tags?post=5103"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}