LIST, EXCUSE THE USE OF ALL CAPS...I'M NOT SHOUTING, JUST MAKING MY COMMENTS STAND OUT. I ALSO APOLOGIZE IN ADVANCE FOR THE LENGTH OF THIS RESPONSE. I have read this forums discussion about inertia these past weeks with increasing amusement. It is truly incredible what conclusions physics students of clearly undergraduate calibre are capable of. I sometimes marvel at the fact that this country is able to produce any physicists with half a brain at all. WHO TAUGHT THOSE "physics students of clearly undergraduate calibre"? MAYBE SOMEONE WITH A "PhD"? I HAVE ALSO READ THIS "forums" DISCUSSION ABOUT INERTIA THESE PAST WEEKS. NOT WITH AMUSEMENT, BUT WITH FASCINATION. PEOPLE HAVE QUESTIONS, AND ON THIS LIST PEOPLE DO THE BEST THEY CAN TO HELP ANSWER THOSE QUESTIONS. APPARENTLY, ONCE YOU HAVE PHYSICS YOU SHOULD KNOW IT AND UNDERSTAND IT THE REST OF YOUR LIFE WHETHER OR NOT YOU UNDERSTOOD IT THE FIRST (OR SECOND) TIME YOU HAD PHYSICS. (COURSE, IF YOU HAD A TEACHER AS GOOD AS CALIN THOMASON.......) To the point however. There have been many comments and claims pertaining to the definition of inertia that attempt to deny any association with velocity, acceleration, and in one instance even mass. One individual declaring himself an authority even goes so far as to declare that inertia is not quantifiable. What utter nonsense. I LIKE HOW INERTIA IS QUANTIFIED BELOW..... May I remind you all that Newtons first law is clearly and precisely described and quantified by Newtons second law. Yes yes, it is true we do not have a ?unit of inertia? per se. That being said, it is absurd to think of inertia as unquantifiable, unvarying, or unassociated with mass and acceleration. Any object has a quantifiable resistance, impedance if you prefer, to a change in its velocity to any other given velocity, and that resistance is reflected clearly and precisely in the amount of force required to achieve that acceleration. DID ANYONE SEE A UNIT FOR INERTIA EXPLAINED ANYWHERE IN HERE BY THE PhD? NO? YOU KNOW WHY? THERE ISN'T ONE!!!!! AND JUST FOR THE RECORD, NEWTON'S SECOND LAW ONLY PERTAINS TO NEWTON'S FIRST LAW WHEN ALL EXTERNAL FORCES ARE EQUAL TO ZERO. IF ALL EXTERNAL FORCES ARE ZERO, THERE IS NO ACCELERATION. IF THERE IS NO ACCELERATION THERE IS NO CHANGE IN VELOCITY. THIS MAY BE APPARENT TO SOME. KEEP THIS IN MIND FOR BELOW. "Newtons first law is clearly and precisely described and quantified by Newtons second law", BUT I DON'T SEE THAT CLEAR AND PRECISE DESCRIPTION EXPLAINED HERE....DOES ANYONE ELSE? THIS WOULD BE A TYPICAL PHYSICS EXPLANATION OF WHAT IS CALLED AN INTANGIBLE CONCEPT. WE (PEOPLE WHO TEACH AND STUDY PHYSICS) USE ONE CONCEPT TO DESCRIBE/EXPLAIN/QUANTIFY ANOTHER. SOME DO NOT BOTHER TO NECESSARILY, OR CLEARLY, DISTINGUISHING BETWEEN THE TWO TERMS WHEN EXPLAINING TO OTHERS. OUR PhD GOES ON TO CLEAR UP WHAT INERTIA IS BELOW AND GETS CONFUSED. THOSE OF YOU WHO HAVE HAD PHYSICS UNDERSTAND HAVING A PHYSICS TEACHER "EXPLAIN" TERMS. THE EXPLANATION SOMETIMES USES TERMS THAT ARE NOT UNDERSTOOD. It will take twice as much force to accelerate a 10 kilo object from a one velocity to another as it will take for a 5 kilo object. Why ??.. the blatantly obvious reason is because the 10 kilo object has twice as much inertia. Likewise, if you have two equal masses and wish to accelerate one twice as much as the other, it will require twice as much force to do so. Again because the inertia of one is twice that of another. You may think of inertia is a mirror image of force. THE WHOLE POINT OF THIS THREAD WAS TO CLEAR UP WHAT MEANS WHAT. ACTUALLY, I THINK IT STARTED WITH EXTENDING AN EXPLANATION OF TOUCH WEIGHT. SINCE MR., OR SHOULD I SAY DR., THOMASON MADE EVERYTHING SEEM SO CLEAR, NO ONE SHOULD FEEL THE NEED TO REPLY. WELL, I LIKE TO LOOK AT WHAT PEOPLE SAY AND I HAVE TO REPLY BECAUSE...... "It will take twice as much force to accelerate a 10 kilo object from a one velocity to another as it will take for a 5 kilo object. Why ??.. the blatantly obvious reason is because the 10 kilo object has twice as much inertia. THE BLATANTLY OBVIOUS REASON IS NOT THAT THERE IS TWICE AS MUCH INERTIA. THERE IS TWICE AS MUCH MASS WHICH IS THE REASON THAT THERE IS TWICE AS MUCH INERTIA. DON G. CLEARLY EXPLAINED THAT MASS AND INERTIA ARE RELATED. THEY ARE. THEY ARE DIRECTLY RELATED. IF YOU INCREASE MASS, YOU INCREASE THE AMOUNT OF INERTIA. HOWEVER, AS DON G. EXPLAINED PERFECTLY, MASS AND INERTIA ARE NOT THE SAME THING. THE CONCEPT OF INTERIA EXISTS BECAUSE OBJECTS HAVE MASS AND IT WAS FOUND THAT BECAUSE THEY HAVE MASS THEY HAVE A "TENDANCY" TO NOT MOVE. NEWTON DID THE BEST HE COULD TO EXPLAIN THIS CONCEPT. AN OBJECT (ALL OBJECTS HAVE MASS) "TENDS" TO STAY AT REST, OR AT A CONSTANT SPEED IN A CERTAIN DIRECTION, UNTIL AN EXTERNAL FORCE ACTS UPON THE OBJECT. THIS "TENDANCY" IS DEFINED AS INERTIA. AS I EXPLAIN TO MY PHYSICS STUDENTS, THIS TENDANCY (INERTIA) IS DIRECTLY RELATED TO MASS. MORE MASS = MORE INTERTIA. Likewise, if you have two equal masses and wish to accelerate one twice as much as the other, it will require twice as much force to do so. IT IS TRUE THAT IF YOU HAVE TWO EQUAL MASSES AND WISH TO ACCELERATE ONE TWICE AS MUCH AS ANOTHER, IT WILL REQUIRE TWICE AS MUCH FORCE. HOWEVER, NOT BECAUSE OF A DIFFERENCE IN INERTIA. Again because the inertia of one is twice that of another. IF THE ACCELERATION WAS EQUAL TO ZERO, THIS IMPLIES THAT THE OBJECT HAS NO INERTIA WHEN IT IS AT REST (ALSO IF IT IS MOVING IN A STRAIGHT LINE AT CONSTANT SPEED). IF ONE NEEDS TO ACCELERATE AN OBJECT TWICE AS FAST, YOU NEED TO APPLY TWICE AS MUCH FORCE TO DO SO. THE OJBECT'S MASS DOES NOT CHANGE, THEREFORE THE OBJECT'S INERTIA IS THE SAME. MR. DR. THOMASON, CHECK THE COLLEGE TEXTBOOK THAT YOU ARE USING. IT SHOULD SAY THAT INERTIA IS ONLY DEPENDANT ON MASS! (UNLESS MAYBE YOU WROTE IT. IF SO, YOU MIGHT WANT TO CHANGE THAT LITTLE PART.) You may think of inertia is a mirror image of force. REALLY, NOW INERTIA IS RELATED TO FORCE? HOW SO? (EXPLAINED BELOW) SO IN THIS PARAGRAPH, MR. DR. THOMASON, YOU SAID THAT INERTIA IS THE SAME AS MASS, AS ACCELERATION, AND AS FORCE. WOW, THAT CLEARS THINGS UP. NO REASON TO HAVE ANY MISCONCEPTIONS ABOUT INERTIA. OBVIOUSLY! YA, RIGHT. NEWTON'S SECOND LAW RELATES MASS, FORCE, AND ACCELERATION BY THE EQUATION F = MA. ACTUALLY, ORIGINALLY, I THINK, HE DEFINED ACCELERATION AS THE RATIO OF FORCE OVER MASS, A = F/M. A LITTLE ALGEBRA GIVES YOU THE SAME F = MA. IF YOU INCREASE THE MASS, FORCE INCREASES GIVEN THAT ACCELERATION STAYS THE SAME. IF YOU INCREASE ACCELERATION, FORCE INCREASES GIVEN THAT MASS STAYS THE SAME. BY SAYING THAT INERTIA IS RELATED TO MASS IS CORRECT. SAYING INERTIA IS RELATED TO ACCELERATION IS NOT CORRECT AND THERE IS NO PROOF OTHERWISE, EVEN WITH MR.DR. THOMASON'S EXPLANATION. IS THERE A UNIT FOR INERTIA? NO. RELATIONSHIP DOES NOT IMPLY EQUALITY. THEREFORE THE UNITS FOR MASS CANNOT BE ASSIGNED TO INERTIA. CALL IT A "TENDANCY". That Newtons second law chooses to express this relationship in terms of force rather then resistance is superfluous to the understanding of the nature of inertia. Force is simply flipside of inertia and likewise. That students are not taught to think in these terms has a reasonable enough explanation, it is for most purposes better to use other physics tools and constructs to describe the various systems we wish too describe. That said, any student of physics should be able to put 2 and 2 together and see the sense in any perspective, especially one so simple, regardless of whether it is usual or not. CAN ONE USE SUPERFLUOUS AND FLIPSIDE IN THE SAME PARAGRAPH? FOR WHAT ITS WORTH, RESISTANCE (IN MECHANICS) IS A FORCE. HOWEVER SINCE MR. DR. THOMASON SAYS THAT WE CAN THINK OF INERTIA AS A RESISTANCE.....WRONG. AGAIN, THIS IS WHY PEOPLE HAVE MISCONCEPTIONS. That students are not taught to think in these terms has a reasonable enough explanation.....YA, THE FACT THAT OTHER PHYSICS TOOLS AND CONSTRUCTS ARE USED TO DESCRIBE VARIOUS SYSTEMS IS USED ALL THE TIME IN SCIENCE. THIS IS A COP-OUT FOR NOT TEACHING. THE FACT THAT "OTHER PHYSICS TOOLS AND CONSTRUCTS" ARE USED TO TEACH AND UNDERSTAND PHYSICS IS TRUE. THE ONLY TIME IT IS SUCCESSFULL IS IF THE TEACHER THOROUGHLY EXPLAINS THE RELATIONSHIP BETWEEN THE "TOOL" AND THE CONCEPT THAT THE "TOOL" IS EXPLAINING. REMEMBER, SOMEONE HAD TO TEACH US 2 AND 2 AND JUST BECAUSE YOU (MR.DR. THOMASON) UNDERSTAND DOESN'T MEAN EVERYONE DOES AND MAYBE YOU ONLY THINK YOU DO. GIVEN YOUR PATIENT EXPANATION ON PHYSICS NOW EVERYONE UNDERSTANDS YOU. THEY MAY NOT UNDERSTAND WHAT YOU SAID, BUT THEY UNDERSTAND YOU. I should perhaps mention that I am a PhD, and teach graduate level applied physics / acoustics and have done so these past 35 years. I would suggest that at least three of the participants who portend a level of authority consider going back for a serious brush up. AND THIS LENDS CREDIBILITY TO YOUR ABUSE? NOT ONE OF THESE PEOPLE "portend"ED (WHO USES THIS WORD) A LEVEL OF AUTHORITY. THEY DID MAYBE STATED WHAT THEIR BACKGROUND WAS, BUT NOT ONCE DID THEY SAY THAT THEIR WORD WAS ABSOLUTE. THESE PEOPLE ARE UNSELFISH AND FRIENDLY PEOPLE CONTRIBUTING TO A DISCUSSION THAT I HOPE DOES NOT END. IT'S DISCUSSIONS LIKE THESE THAT DEVELOP IDEAS THAT TURN INTO SOLUTIONS TO DIFFICULT PROBLEMS. AS AN EDUCATOR, YOU SHOULD ONLY HOPE FOR DISCUSSIONS LIKE THIS. YOU MIGHT EVEN LEARN SOMETHING! I do not intend to get involved in any discussion here, and have no intention of fielding any flurry of protests and questions. Dig back into your college texts and think about what you read there. WHY WRITE ANYTHING AT ALL? Seasons Greetings HMMMMM. GOTTA WONDER ABOUT PEOPLE WHO SLAM OTHERS AND FOLLOW IT UP WITH "SEASONS GREETINGS". Calin Thomason. SARAH, DON, MARK, OTHERS WHO HAVE CONTRIBUTED (SORRY IF I MISSED SOMEONE) AND OTHERS WHO ARE FOLLOWING THIS THREAD....THANK YOU FOR YOUR CONTRIBUTIONS! PAUL CHICK. JUST A HIGH SCHOOL PHYSICS AND CHEMISTRY TEACHER WITH AN INTEREST IN PIANO TECHNOLOGY. PROUD IN THE USA! PAUL CHICK'S PIANO SERVICE PLAINVIEW, MN, 55964 USA
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