ydoaPs Posted August 23, 2005 Posted August 23, 2005 26.(II) Estimate how many hours it would take a runner to run (at 10 km/h) accross the United States from New York to California 28.(II) Estimate the number of liters of water a human drinks in a lifetime. 30.(II) Make a rough estimate' date=' for a typical suburban house, of the % of its outside wall area that consists of window area.[/quote'] no information is provided to help solve any of those problems. i looked through the chapter too. and no info that helps. anyone know any statistics to help?
Klaynos Posted August 23, 2005 Posted August 23, 2005 well first one get an atlas and make a rough guess (depending how annoying you feel your teacher is you might wanna think about time to sleep too). Second one find out the average an adult needs to drink/day and average life span - might wanna think about something to deal with less liquid when a kid too Find a photo of an "average" house and work it out :s...
ydoaPs Posted August 23, 2005 Author Posted August 23, 2005 i don't have an atlas. anyone know the distance off the top of your head? aren't you supposed to drink like 2 liters a day? no clue on average life span. no clue on the last one.
ydoaPs Posted August 23, 2005 Author Posted August 23, 2005 eh, i think i can get away with skipping them and yelling at the teacher for using such a crappy book.
mezarashi Posted August 23, 2005 Posted August 23, 2005 How are those questions even physics related. LOL, how much water do you drink in a life-time? Isn't that more like.... I don't know what it is.
Martin Posted August 23, 2005 Posted August 23, 2005 eh, i think i can get away with skipping them and yelling at the teacher for using such a crappy book. in my humble opinion, Mr. Stick, the exercises are intended to get students used to making rough order-of-magnitude estimates being able to do that----get a reasonable rough estimate with very little information to go on ---- is a talent that good physicists cultivate, it is useful in other branches of science too.
ydoaPs Posted August 23, 2005 Author Posted August 23, 2005 in my humble opinion' date=' Mr. Stick, the exercises are intended to get students used to making rough order-of-magnitude estimates being able to do that----get a reasonable rough estimate with very little information to go on ---- is a talent that good physicists cultivate, it is useful in other branches of science too.[/quote'] that is what the exercises are for, but you do need some information!
Martin Posted August 23, 2005 Posted August 23, 2005 the problem to estimate how much water a human drinks in a lifetime is a very good exercise because there is no correct answer except order-of-magnitude it is BECAUSE people vary a lot that it is a good exercise, because you can see right away that all you need to do is get it within a factor of 10 or 100. You learn by this how to be reasonable and not obsessed with numerical precision when you do estimates. You had better do it Yourdad, it is not as dumb as it seems.
ydoaPs Posted August 23, 2005 Author Posted August 23, 2005 the problem to estimate how much water a human drinks in a lifetime is a very good exercise because there is no correct answer except order-of-magnitude it is BECAUSE people vary a lot that it is a good exercise' date=' because you can see right away that all you need to do is get it within a factor of 10 or 100. You learn by this how to be reasonable and not obsessed with numerical precision when you do estimates. You had better do it Yourdad, it is not as dumb as it seems.[/quote'] how do you do such things with absolutely no information given?
Martin Posted August 23, 2005 Posted August 23, 2005 that is what the exercises are for, but you do need some information! OK it is 3000 miles from NY city to San Francisco, as the crow flies. you have to know how to turn that into kilometers and to get a rough estimate of how much longer the road trip is than the crow flight
Martin Posted August 23, 2005 Posted August 23, 2005 1mile=xkilometers? Nobody tell him Mr. Stick you dont have to use kilometers. The answer only needs to be the HOURS the runner takes. the rule is USE WHAT YOU KNOW do you know a jogging or easy longdistance running speed in MILES PER HOUR? Like, is it maybe a tenth of highway driving speed? Come on, mobilize what you know. It doesnt have to be numerically PRECISE, just reasonable. A working physicist will constantly be doing this kind of rough estimate based on imperfect sketchy info.
ydoaPs Posted August 23, 2005 Author Posted August 23, 2005 you have to know how to turn that into kilometers Mr. Stick you dont have to use kilometers. The answer only needs to be the HOURS the runner takes. tricksy hobbitses!
Iceberg_Blow Posted August 23, 2005 Posted August 23, 2005 i think i have the same phyics book. its dumb and blue and has (II) by questions to show how hard they are. its by some author who starts wit a g. its a bad textbook lol
ydoaPs Posted August 23, 2005 Author Posted August 23, 2005 the roman numerals are for the AP system. mine is Physics: Principles With Applications Sixth Eddition by Douglas C. Giancoli
Iceberg_Blow Posted August 23, 2005 Posted August 23, 2005 I no the book i have has the same author, and the q u mentioned sounds like some of the ones in my book
mezarashi Posted August 23, 2005 Posted August 23, 2005 yourdadonapogos, beware! Martin is actually your physics teacher in disguise!
Severian Posted August 23, 2005 Posted August 23, 2005 I agree with Martin. These questions are designed to see if you can use your head for making order of magnitude calculations - they are not meant to be exact to the 10th decimal place. This is a really useful skill in studying science. I am amazed how many students don't realize that their answer is wrong, even though they have just 'proven' that the hydrogen atom is larger than the size of the observable universe. Frankly, if you can't do these questions without looking up info on the web, you should be flunked.
swansont Posted August 23, 2005 Posted August 23, 2005 Nobody tell him Mr. Stick you dont have to use kilometers. The answer only needs to be the HOURS the runner takes. the rule is USE WHAT YOU KNOW do you know a jogging or easy longdistance running speed in MILES PER HOUR? Like' date=' is it maybe a tenth of highway driving speed? Come on, mobilize what you know. It doesnt have to be numerically PRECISE, just reasonable. A working physicist will constantly be doing this kind of rough estimate based on imperfect sketchy info.[/quote'] To be fair, the question does say "at 10 km/h" Another thing you need to do in physics is get to know simple conversions. 1 inch = 2.54 cm, and all that. 10 km = 6.2 miles, as anyone who runs races can tell you, which puts you smack-dab in the middle of Martin's 1/10 of highway driving speeds. Another reason to learn this is to be able to estimate reasonable answers, so you don't blindly believe what your calculator tells you, e.g. "the mass of the frog is 1024 kg" One of the grading policies in place when I taught at nuke school was that a GCE - gross conceptual error - was grounds for losing all points on a problem. (a lesser offense was a CE - conceptual error). An example of that was a physically unreasonable answer.
insane_alien Posted August 23, 2005 Posted August 23, 2005 yeah just take a wild guess that seems to be about right. no calculations.
ydoaPs Posted August 23, 2005 Author Posted August 23, 2005 i can't figure out how to do the last one. i have no idea where i would get the info.
timo Posted August 23, 2005 Posted August 23, 2005 Are there no houses with windows close to where you live?
Klaynos Posted August 23, 2005 Posted August 23, 2005 Are there no houses with windows close to where you live? And I'm sure he knows how to work out areas :s ||edit Orders of magnitude are great, alot of the time at uni it's all we're required to work out Except in assessed work oc
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