measurement notes 2013

8/13/2019 Measurement Notes 2013

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MEASUREMENT

In Grade 8 a student should

1. understand the difference between quantity and unit.2. know the SI units of various quantities.3. know the meanin and symbols of kilo! me a! i a! tera! milli! centi!

micro! nano and "ico.#. convert units for a quantity.$. understand the orders of ma nitude for which multi"les and submulti"les

should be used.%. be able to use the metre rule to measure len th.&. be able to measure the area of a re ular rectan ular sha"e8. be able to measure the volume of rectan ular blocks as well as irre ular ob'ects such as

stones! lass sto""ers etc.(. be able to use the measurin cylinder! "i"ette! burette and tri"le)beam balance.1*. be able to take very small measurements by usin multi"licative methods e + thickness of

sheet of "a"er, volume of dro" of water etc

QUANTITIES AND UNITS

- hysical /uantity is e0"ressed as the "roduct of a numerical value and a "hysical unit.

e. . he tallest livin man is Sultan osen. e is 2!$1 m tall and still rowin .

ow tall are you4 5and still rowin 6.

S.I. - SYSTEME INTERNATIONAL D UNITES

he system of measurement used in most "arts of the world is called the Systeme International7 unites 5SI units6.

In this system the 3 most im"ortant units for rade 8 are+

The metre (m = the unit of len th!The "ilo r#m (" = the unit of m#$$!The $e%on& ($ = the unit of time!

hese 3 units are called '#$e unit$.

9ther units like m 2 and k .m )3 can be made u" from the base units and are called &eri e& unit$ .

(E)ten$ion! here are four other base units+ #m*ere for current! +el in for tem"erature! %#n&el# forluminosity and mole for amount of a substance.6

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:om"lete the table.

QUANTITY SI UNIT OT,ER UNITS (e)ten$ion!ounce! "ound! ton

year! hour metre 5m6 inch! yard! mile

area acrecubic metre 5m 36 ;itre! allon


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here are other "refi0es+

Billion times > me a 5B61*** million times > i a 5G6Billion million times > tera 5 61?million > micro 5C61?1*** million > nano 5n6

1?million million > "ico 5"6

O1ERS O/ 23

Instead of usin "refi0es for very lar e or very small numbers we can use "owers of 1* to re"resentmulti"les or submulti"les.

ower of 1* refi0

1* 1 > 1* deca 71*3 > 1* 0 1* 0 1* > 1*** kilo k

1*%

> 1* 0 1* 01* 0 1* 0 1* 0 1* me a B1* ( > 1*01*01*01*01*01*01*01*01* i a G

1*12 > 1*01*01*01*01*01*01*01*01*01*01*01* tera1* )1 > 1?1* deci d1* )2 > 1?1** centi c1* )3 > 1?1*** milli m1* )% > 1? 1 *** *** micro C1* )( > 1? 1*** *** *** nano n1* )12 > 1? 1*** *** *** *** "ico "

DSE 9< BD; I ;E -@7 SDFBD; I ;E D@I S

5 a""ro0imate measures 61* )12 "ico radius of o0y en atom > & "m1* )% micro si e of a bacterial cell > 1Cm1* )3 milli width of cell"hone > 8 mm1*3 kilo distance to Gauten > 1$** km1*% me a distance to moon > #** Bm1* ( i a diameter of sun > 1 Gm1*12 tera distance "luto to sun > % m

Ae choose units and multi"les of units so that the numbers used will be easy to work with incalculations e + the len th of climbin ro"e is about #*m but the distance to 7urban is 2*** km andthe len th of a matchbo0 is $* mm.

E0tra conversions (e)ten$ion 4or"!

1. %!# Gm > ...km 2. *!#$ m > C

3. %$8(!# "m > .mm #. *!**$ bytes > ..Gbytes

$. # 0 1* )# s > ...ms %. & 0 1* 1* m > m

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MEASURIN5 6OLUME

he volume of an ob'ect is a measure of the s"ace it occu"ies.

1. Kolume of a rectan ular block o find the volume of a rectan ular block we measure its len th! breadth and hei ht and usethe formula+ K > l 0 b 0 h

K > l 0 b 0 h

>

2. Kolume of irre ular solid ob'ect 5 e . a stone 6

5a6 7is"lacement of water in a measurin cylinder ut some water in a measurin cylinder and take thereadin .Jemember to avoid "aralla0 and also to take thereadin at the 'ottom of the meni$%u$.ut the stone into the water and take the readin a ain.he difference between the 2 readin s should be thevolume of the stone. (V = V 2 V 1 = 14 10 = 4 ml)

5b6 7is"lacement of water from a Eureka can.


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Me#$urin M#$$

Mass is the quantity of matter in an object.

1. Electronic Scales. 5Karious ty"es. Dsually measure to *!1 or *!*1 accuracy.6

2. ri"le beam balance. 5-ccurate to *!1 .6

hese are called LbalancesM because theo"erator moves the various wei hts on thethree arms in order to balance the turninforces about a "ivot. Ahen balanced thereadin of the mass of the ob'ect can bemade.

he readin on the tri"le beam balance is+

1** arm > .

1* arm > .

7i it arm > .

Tot#l m#$$ = 7777777

Me#$ure $m#ll #lue$ u$in l#r e num'er$

Arite down a short method of how one mi ht measure the followin . hen do the first one. 5Hourteacher will do the second for you.6

e. .1 hickness of a "a e in your te0tbook.

e. .2 Kolume of a "a"er cli".

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Me#$urin hei ht u$in $h#&o4$ #n& *ro*ortion$

- len th of an ob'ects shadow 5;6 is always in direct "ro"ortion to its hei ht 5 6.

> h ; l

If the small ob'ect is a 1 metre ruler then LhM can be re"laced by 1

he equation can then be substituted and rearran ed to become+

> ;? l

r#%ti%#l e)#m*le8

-im+ o find the hei ht of a ru by "ole on the iley Jees

Bethod+ Go to ru by field Stand metre rule u"ri ht. Beasure len th of shadow of metre rule 5 l6. Jecord. Beasure len th of shadow of ru by "ole 5;6. Jecord.

Jesults+ l > ; > ..

:alculation+

> ;? l

>

:onclusion+ he hei ht of the "ole is .

8

h

; l


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DENSITY

7ensity is defined as mass per unit volume.

Den$it9 = M#$$:6olume & = m:6

he SI unit is kilo ram "er cubic metre 5k .m )36 but we usually use .%m -; .

e. . Ahat is the density of a silver if %3 of it has a volume of % cm 34

d > m?K > %3?% >23< .%m -;

-nswer the followin questions showin all your workin . Set out neatly.

1. Ahat is the density of coal if 1$ cm 3 of it has a mass of 2& 4

2. :alculate the mass of mercury in 2$ cm 3 of it. Bercury has a density of 13!% .cm )3.

3. Ahat is the volume of old in a crown if it has a mass of 2 k 4 Gold has a density of1(!3 ?cm 3.

(

d

m

K

he density of water isabout 1!* .cm )3.


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#. Ahat mass of air is in a room if its density is 1!2% k ?m 3 and the dimensions of the roomare 1* m by 12 m and it has a hei ht of # m4

$. - rock of mass 8% is lowered into some water in a measurin cylinder. he level ofthe water rose from #* cm 3 to &8 cm3. Ahat was the density of the rock4

%. - rectan ular block of co""er has a density of 8!(# .cm )3 and a mass of 112 . Ahat isthe len th of the block if it has a hei ht of *!( cm and a breadth of 2!8 cm4

&. - neutron star consists of matter with a density of about $ 0 1*1#

.cm)3

. If a teas"oon ofit is $ cm 3! what would be the mass of a teas"oon of matter from a neutron star4

8. - %!* m rectan ular rod has the same breadth and width. If it was made of iron 5density

&!8 .cm)3

6 and had a mass of 1# k ! what was its breadth and width4

1*


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/OR>E

- force is a "ush or a "ull.

- force chan es the s"eed! direction and?or sha"e of an ob'ect.

Dnit+ newton 5@6

1ei ht8 this is the ravitational force which acts on an ob'ect on or near the surface of a "lanet ormoon.

9n earth the ravitational field stren th 5 6 is 1* newtons "er kilo ram 51* @.k )16

e. . - 2 k mass on earth wei hs 2 0 1* > 2* @

- #** mass on earth wei hs *!# 0 1* > # @

9n the moon the ravitational field stren th is 1?% of the earth.

e. - 3 k mass on the moon wei hs 3 0 51*?%6 > $ @

:om"lete the sentences+

- k mass wei hts $* @ on earth.

- 3** k moon bu y has a mass of . on the moon.

- 2#* tin of food will wei h .. on the moon.

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1 ) Out$i&e ?#4$ + used to take e0ternal measures ofob'ects2 ) In$i&e ?#4$ + used to take internal measures ofob'ects3 ) De*th *ro'e + used to measure the de"th of ob'ects# ) M#in $%#le 5cm6$ ) M#in $%#le 5inch6% )6ernier 5cm6& )6ernier 5inch68 ) Ret#iner + used to block movable "art

KEJ@IEJ :-;I EJS and BI:J9BE EJS. 5 E)ten$ion 4or"!

1. Kernier :ali"ers can measure accurately to *!1 mm.

Kernier Scalese. .1 e. .2

he len th is 3!3 mm. he len th is .

2. Bicrometers measure to an accuracy of 1 micrometer 5*!*1 mm6.

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Sleeve reads full mm >

Sleeve reads N mm >

himble reads >

otal measurement >

Sleeve reads full mm > 12Sleeve reads N mm > *!$himble reads > *!1%Tot#l me#$urement = 2@< mm

measurement notes 2013

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