It's Saturday night, and most people are out socializing or partying, or spending time with their families, or even working at an off-hours, demanding job. I am doing my physics problems. Take that as you will; I may be a pitiable soul who has no life, or I am highly dedicated (or both). I haven't done anything with it in two weeks, due to the convention, illness, and the need to clear my studio desks. Tonight I was able to go back to the important stuff, since I have finally vanquished the piles of papers, magazines, bills, and correspondence.

So, back to the sliding blocks on the inclines. Here's one in British units, featuring a 96 lb. weight being pulled up a 45 degree angle (quite a job, you would need a simple machine or two to handle it, but they're off-camera in this problem). Find the acceleration and so forth. I calculate the "normal" and parallel force components of the weight under inclined plane gravity, but then I realize I've forgotten how to do this kind of problem. Arggh! Physics panic! It's late at night. There is no one I could reasonably call. E-mail is too slow (they have to pick it up and answer it, which they certainly won't do on Saturday night) and Friendly Scientists don't waste time in internet relay chat. I hate weekends sometimes. Outside my windows, icy freezing rain is falling.

I flounder around scribbling on my paper, trying to figure out how the book got the answer it did. There is something simple I've forgotten. What do I do? Give up working this problem and go drink some soymilk or do some pointless websurfing? Do some art? Go to bed? None of these are options. I must get a grip. I have resources. The grip I get is on my brilliant yellow "physics problem tutor" book, which was so unhelpful many months ago. Now it is a welcome rescue. Books are patient. Books are kind. Books don't care what time of day or night it is. Nor do they make snide remarks about your lack of lifestyle. Here's one just like that problem, explained on page 68. I have the components, right. But I have to remember that the pulling force is opposed by the downward force of the sliding weight on the incline (friction is disregarded here) so the net result force causing acceleration will be less. And with that British system, the mass isn't 96 pounds. That's the weight. The mass is 96 pounds divided by 32 feet per second², which is 3 "slugs." So that's what goes into the Newtonian equation: resultant force and slugs. Now back to slugging it out with weight, movement, mass, and gravity.

Posted at 3:17 am | link