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MEASURING WEIGHT & MASS (teach & measure)

on Sep 20, 2011

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Addresses the ideas of weight and mass, explains how units of each are derived, and explains how each is measured.

Addresses the ideas of weight and mass, explains how units of each are derived, and explains how each is measured.

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MEASURING WEIGHT & MASS (teach & measure)Presentation Transcript

• MEASURING WEIGHT AND MASSMoira Whitehouse PhD
• MEASURING WEIGHTTO MEASURE MOST ANYTHING ONENEEDS SOME TOOL WITH WHICH TOMEASURE AND A STANDARD UNITOF MEASUREMENT.
• •THE TOOL WE USE TO MEASUREWEIGHT IS A SPRING SCALE.•THE STANDARD UNITOF MEASUREMENTUSED IN SCIENCE ISTHE NEWTON.
• •BEFORE SERIOUS TALK ABOUT THESPRING SCALE, LET’S REVIEW THISIDEA CALLED WEIGHT.•YOU SHOULD REMEMBER THATTHE WEIGHT OF AN OBJECT IS AMEASURE OF HOW HARD GRAVITYIS PULLING ON THE OBJECT.•THE HARDER GRAVITY PULLS ONSOMETHING, THE MORE IT WEIGHS.
• •WHEN WE PICK UP ANYTHING WEARE WORKING AGAINST GRAVITY.•IF WE FOUND OURSELVES ON THEMOON WHERE THE GRAVITY WASLESS, WE WOULD SUDDENDLY SEEMTO BE A LOT STONGER.
• •KNOWING THAT WEIGHT DEPENDSON GRAVITY WE CAN SEE THAT ANYTOOL TO MEASURE WEIGHT MUSTSOMEHOW ACCOUNT FOR EARTH’SGRAVITY.•THE SPRING SCALE DOESTHAT BY HAVING A SPRINGTHAT IS ADJUSTED TO BEJUST AS STRONG AS THEPULL OF EARTH’S GRAVITY.
• •THE PROCEDURETOMEASUREWEIGHTIS TO SUSPENDTHE OBJECT FROMA SPRING SCALEAND READ THEWEIGHT INNEWTONS (n)FROM THE SCALE
• WE NEEDED TWO THINGS TOMEASURE WEIGHT, ONE WAS ATOOL AND THE OTHER WAS:TO MEASURE MOST ANYTHING ONENEEDS SOME TOOL WITH WHICH TOMEASURE AND A STANDARD UNITOF MEASUREMENT.•THE UNITS USED TO MEASUREWEIGHT IN THE METRIC SYSTEMARE NEWTONS (n).
• •SO WHAT IS THIS UNIT OFMEASUREMENT THAT IS NAMED FORTHE GREAT SCIENTIST ISAAC NEWTON?•LIKE OTHER UNITS IN THE METRICSYSTEM, THE NEWTON IS DERIVEDFROM THE METER AND BY USING THEMASS OF WATER, THE EARTH’S MOSTCOMMON COMPOUND. (ONE 10 MILLIONTH OF THE DISTANCE FROM THE NORTH POLE TO THE EQUATOR)
• THIS MUCH WATER 1 GRAM 100 GRAMS X 100 EQUALS = AND = ONE NEWTON IN EARTH’S GRAVITY
• •WITH THAT BIT OF INFORMATIONABOUT THE SPRING SCALE AND THENEWTON, LET’S GET SOMEPRACTICE READING A SPRINGSCALE. •THE RED SCALE IS USED TO MEASURE LIGHTER OBJECTS AND HEAVIER OBJECTS CAN BE WEIGHED WITH THE BLUE SCALE.
• •REMEMBER, IT IS IN EARTH’SGRAVITY THAT ONE NEWTON ISEQUAL TO ABOUT 100 GRAMS.•SO, IF THE VALUE OF GRAVITYCHANGED, SAY ON ANOTHERPLANET, THE VALUE OF THENEWTON WOULD ALSO CHANGE.•THAT OFTEN MAKES THE CONCEPTOF WEIGHT UNSATISFACTORY FORSCIENTIFIC WORK.
• •FOR THEIR WORK, SCIENTISTSNEED INFORMATION ABOUT STUFFTHAT DOES NOT CHANGE ASGRAVITY CHANGES.•AND THEY FOUND IT IN THECONCEPT CALLED.... MASS.
• MEASURING MASS• AGAIN, TO MEASURE MOSTANYTHING ONE NEEDS SOME TOOLWITH WHICH TO MEASURE AND ASTANDARD UNIT OF MEASUREMENT.
• •THE TOOL WE USE TO MEASUREMASS IS A BALANCE SCALE.•THE STANDARD UNIT OFMEASUREMENT USED IN SCIENCE ISTHE GRAM.
• •BEFORE GOING INTO THE NITYGRITTY OF MEASURING MASS, WENEED AN UNDERSTANDING OF JUSTWHAT MASS IS.•MASS IS THE AMOUNT OFMATTER IN AN OBJECT.
• •MASS IS DIFFERENT THAN EITHERSIZE OR VOLUME.•THE OBJECT ON THE LEFT, ALTHOUGHMUCH BIGGER, HAS JUST THE SAMEMASS AS THE TWO SMALL ROCKS ONTHE RIGHT.
• •MASS IS MORE USEFUL TO SCIENTISTSTHAN WEIGHT BECAUSE AN OBJECT’SMASS REMAINS CONSTANT REGARDLESSOF THE AMOUNT OF GRAVITY. •THE REASON THAT THE MASS OF OBJECTS ON A BALANCE SCALE IS NOT AFFECTED BY CHANGES IN GRAVITY IS THAT THE SAME GRAVITY IS PULLING ON BOTH SIDES OF THE BALANCE.
• •IF EACH TRAY HAS THE SAMEAMOUNT OF MATTER...REGARDLESSOF SHAPE OR VOLUME.GRAVITY PULLS EQUALLY ON EACHOF THEM AND THE TRAYS STAYBALANCED.
• •BUT IF ONE OBJECT HAS MORE MASSTHAN THE OTHER:YOU KNOW WHAT’S GOING TO HAPPEN.
• •SURE, THE MORE MASSIVE OBJECT,BEING PULLED HARDER BY GRAVITY,WILL GO DOWN AND THE LESSMASSIVE OBJECT WILL GO UP.
• •IF WE BALANCE AND UNKNOWNOBJECT IN THE RED TRAY WITHKNOWN MASSES IN THE YELLOW TRAYWE WILL LEARN THE MASS OF THEOBJECT IN THE RED TRAY.
• •BUT WHERE DO WE FIND THESE“KNOWN” MASSES?WE USE PIECES OF BRASS MARKEDWITH THEIR MASS AS STANDARDUNITS OF MASS.
• •LIKE THESE:
• •WE HAVE THE TOOL (A BALANCESCALE) AND THE STANDARD UNIT (THEGRAM), THE ONLY OTHER THING WENEED TO FIND THE MASS OF ANOBJECT IS A PROCEDURE.•THE PROCEDURES IN THE FOLLOWINGSLIDES ARE BASIC, BUT THEY WORK.
• 1. PLACE THE OBJECT IN ONE TRAY.
• 2. PLACE THE LARGEST MASS IN THEOTHER TRAY.
• •THE 500g MASS IS THE GREATERTHAN THE MASS OF THE PUMPKIN, SOREMOVE IT AND PLACE THE SECONDLARGEST PIECE OF STANDARD MASS.
• 3. PLACE THE SECOND LARGEST MASSIN THE OTHER TRAY.
• •THE 200g MASS IS ALSO GREATERTHAN THE MASS OF THE PUMPKIN, SOREMOVE IT AND PLACE THE THIRDLARGEST PIECE OF THE STANDARDMASS ON THE TRAY.
• 3. PLACE THE THIRD LARGEST MASS INTHE OTHER TRAY.
• •AH, THE 100g MASS IS LESS THAN THEMASS OF THE PUMPKIN, SO LEAVE ITAND ADD THE NEXT LARGEST PIECE OFSTANDARD MASS ON THE TRAY.
• OK, THE 100g AND 50g MASSES AREEQUAL TO THE MASS OF THEPUMPKIN.
• •IT MAY TAKE A FEW MORE STEPS TOEXACTLY BALANCE THE MASS OF YOUROBJECT.•KEEP USING THE SAME PROCEDURE:ADD THE NEXT LARGEST UNIT AND IFTHAT IS TOO MUCH, REMOVE IT ANDSELECT THE NEXT LARGER UNIT.
• •WHEN THE OBJECT AND THE MASSUNITS ARE BALANCED, LINE UP THEMASS UNITS FROM THE LARGEST TOTHE SMALLEST.•TOTAL THE VALUES OF THE THE MASSUNITS AND BINGO, YOU KNOW THEMASS OF THE OBJECT.
• •THERE ARESOME BALANCE SCALESWITH SLIDERS THAT CAN BE USED TOMOVE GRADUATED AMOUNTS OFMASS TO BALANCE THE OBJECT.•THESE ALLOW THE MASS OF THEOBJECT TO BE READ DIRECTLY FROMTHE SLIDERS.
• •MORE ADVANCED BUT EVEN MOREDISTANT FROM “BALANCING” MASSES,IS THE TRIPLE BEAM BALANCE.
• •YOU READ THIS SCALE BY NOTINGWHERE THE SLIDER POINTERS AREAND TOTALING THOSE NUMBERS. RIGHT, 161 GRAMS
• THERE YOU HAVE IT:MEASURING WEIGHT AND MASS
• •STUDY •YOU CANSCIENCE AND LEAP HIGHWHEN YOU AND WEIGHGROW UP YOU LESS, BUTMAY GET A DON’TCHANCE TO FORGET, YOURGO THE MASS WILLMOON STILL BE THEWHERE: SAME.