Using your common sense to solve a physics problem.

Perhaps you could start with a simpler question, like, "Is there sufficient information to solve the problem? Explain why or why not."--Percy

No one's engaged the problem yet - who are you irritated at? Do you often find yourself arguing with department store mannikins? Except for the tedium of going through the actual steps, your problem is too simple. I'm more interested in the solution to Crash's problem. I can't remember the equations for rotational momentum or energy, I couldn't find them on the web, and now it's bothering me, I want the answer.--Percy

I see your message has already drawn some replies, so maybe this is redundant, but Lam posted the problem to illustrate that common sense can often lead you astray. There are many types of problems for which the answers are unintuitive.I think it's great that you want to solve the problems posed by Crash and Lam, but solving the problems wasn't why they posted them. They posted them to illustrate the great error in your characterization of an entire class of people as "jerk scientists" who with all their education and training can be matched with simple common sense.It would be nice if we could better equip scientists for their profession by providing them less education so that their common sense wasn't suppressed by all those darn niggling facts, but gee, things just don't turn out to work that way. If they did then you would have already solved these problems, but you haven't, have you? And that's because common sense is a poor substitute for knowledge.You recently wrote that you didn't have the opportunity to go to college, but that you feel you make up for it by learning on your own. I think you'll find that the more you learn, the more uncommon your sense will be, but you'll have improved analytical skills and a much broader base of knowledge upon which to draw, and you'll be all the better for it.--Percy

But isn't $45K Canadian around the $30K American that RiverRat mentioned?I don't think $30K American is a salary being offered to engineering graduates anywhere in the states. I don't know about recently (I got out of management a while back), but 10 years ago we were offering starting salaries of around $50K to recent masters graduates in software engineering. With inflation I imagine it would be around $65K now. A bachelors degree might draw $50K today. A 2-year tech college graduate might get offered around $30K to do tech-support/computer-maintenance type work, but I can't imagine anything less than that, though perhaps in regions of the country far from hi-tech centers...--Percy

Nothing like examples from the real world, only about 300 miles from you. July 17, 1981.--Percy

I'll let Lam be the final judge, but it looks right to me. Are you a jerk scientist or a common sensist? --Percy

Once you've been provided the data and the equations, the rest is just common sense. There's more than one way to approach the solution, but they're all just common sense.I can't tell if you're expressing things in a funny way or if you're misunderstanding something, so I'll just say this:

• There's a component of the force of gravity parallel to the slope pulling the car down the slope.
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• There's a force resisting the car's progress down the slope that is equal to the kinetic coeeficient of friction multiplied by the component of the force of gravity that is normal to the slope.
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• The difference between these two forces is the net amount of force on the car. If the net stopping force is larger, then the car will decellerate, while if the falling down the slope force is larger then the car will accelerate.
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• If you solve the problem symbolically before plugging in the values, you'll find that mass drops out and isn't a factor.

That last point is counterintuitive, isn't it? That's why this problem is such a wonderful example of the insufficiency of common sense for much of problem solving. You've discovered that your common sense has failed you, and that your lack of knowledge has become a significant obstacle. You've been reduced to slogging your way through what is actually an extremely simple problem in mechanics. And you can't even cite your lack of college training on this one, because this is basic high school physics.You've obviously learned a lot and come a long way on just your own inner resources, and you deserve lots of credit for that. But human intelligence is often given far more credit than it deserves. We're definitely the smartest creature on the planet, but a lot of our intellectual advantage derives from the base of knowledge we've accumulated over the last 10,000 years. Take away our ability for each generation to pass its knowledge on to the next and our big advantage diminishes almost completely. That's why for most of human existence it has been bare subsistence.So while your accomlishments deserve praise, keep in mind that as much as Newton you are standing on the shoulders of those who came before.--PercyThis message has been edited by Percy, 09-24-2004 04:35 PM

Lamba usually refers to wavelength.--Percy

Uh, well, yes, precisely. Are you following the Bible or not? If you're following the Biblical account where the flood water persisted for months after the rain stopped, then why are you arguing that the flood would have gone away when the rain stopped?Don't people with common sense like yourself usually think more logically than this?--Percy