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Natuurwetenskappe

Graad 9

Energie, kragte en masjiene

Module 22

Drywing

Werkverrigting (arbeid) is belangrik, maar die SPOED waarteen die werk gedoen word, is eweneens belangrik.

Aktiwiteit 1:

Om die begrip drywing te kan verduidelik en om drywing te kan bereken

[lu 2.3; lu 2.4]

DRYWING = ARBEID / TYD

Ons meet dit in J/s of beter bekend as Watt (W)

1J per sekonde lewer 1 Watt drywing

  • Die term Watt is afgelei van die naam van James Watt wat die stoomenjin verbeter het.
  • Elektrisiteit in jou huishouding word gemeet in kilowatt-uur ( kWh ).
  • Een kilowatt-uur is die energie-uitset deur ’n 1 kW toestel in een uur.
  • Hoe langer so ’n toestel aangeskakel bly, hoe meer energie word verbruik. So sal ’n 2 kW-verwarmer wat drie ure aangeskakel bly 6 kW energie verbruik.
  • Voltooi: …… kW per uur x ….. uur = 6 kW.
  • Die koste vir ’n kWh wissel, maar is in die Wes-Kaap tans ongeveer R0.35.

Opdrag:

Meet jou eie drywingsvermoë

  • Gaan na ’n stel trappe in julle skoolgebou en meet die traphoogte.
  • Vermenigvuldig dit met die aantal trappies.
  • Bepaal jou GEWIG.
  • Hardloop teen die trappe uit en neem die tyd in sekondes.

Voltooi die volgende tabel:

Aspek Meting
Traphoogte .
Massa
Gewig
Werk gedoen: F x s
Tyd

VRAE

1. Wat was jou drywing?

2. Waarvoor staan

a) Kilowatt?

b) Kilowatt-uur?

3. Vind uit wat die drywingskrag van die gemiddelde motor (gestel jou onderwyser s’n) is.

4. Sal jy kans sien om jou onderwyser se motor huis toe te stoot?

5. Waarom sal dit makliker wees as die enjin dit doen, selfs al sou jy die tyd hê en jou maats jou help?

6. Bereken wat ’n 3 000 W-verwarmer wat vir ’n maand lank (Julie) 4 ure per dag aangeskakel was jou sal kos teen ’n tarief van R0,35 per kWh.

Assessering van BEREKENING van DRYWINGSVERMOË

Kon jy kennis toepas en berekeninge doen?

[LU 2.3; LU 2.4]

Aktiwiteit 2:

Om navorsing oor drywing te doen en om relevante berekeninge te maak

[lu 1.1; lu 1.2; lu 2.2; lu 2.4]

Vind uit wat 1 kWh elektrisiteit in jou munisipale area kos.

Gestel jy gebruik die volgende toestelle deur die loop van die dag:

  • Rekenaar vir 2 ure
  • Televisie vir 3 ure
  • Lamp vir 4 ure
  • Ketel vir 15 minute
  • Stoof vir 45 minute
  • Haardroër vir 15 minute
  • Stel vas wat die gemiddelde drywing vir elk van hierdie items is deur op die apparate se aanwysings te kyk. Voltooi die tabel.
Elektriese toestel Drywing (kW)
Rekenaar
Televisie
Lamp
Ketel
Stoof
Haardroër

Voltooi nou die volgende tabel vir jou kosteberekening:

TOESTEL DRYWING (kW) soos hierbo TYD gebruik(ure) Energie verbruik (kW/h) Koste @ R1,50 per uur
Rekenaar
Televisie
Lamp
Ketel
Stoof
Haardroër

VRAE

1. Watter gevolgtrekking kan jy maak?

2. Besef jy dat energie spaarsamer gebruik behoort te word? Gee jou eie mening hieroor.

3. Bereken die volgende:

a) ’n Bergklimmer met ’n massa van 75 kg klim ’n krans van 320 meter hoog in 20 minute uit. Bereken sy drywing.

b) ’n Groot kas van 150 kg moet tydens ’n trekkery met trappe van so 5 m hoog opgedra word.

  • Hoeveel werk word gedoen?
  • Wat is die werkers se werkverrigting as twee mans dit binne 10 minute doen?

Assessering van NAVORSING oor toestelle

Kon jy die inligting bekom en die berekenige doen?

Kon jy kategoriseer?

[LU 1.1; LU 1.2; LU 2.2; LU 2.4]

Assessering

LU 1

Wetenskaplike Ondersoek

Die leerder is in staat om met selfvertroue op weetgierigheid oor natuurlike verskynsels te reageer, en om binne die konteks van wetenskap, tegnologie en die omgewing verbande te ondersoek en probleme op te los.

Dit word bewys as die leerder:

1.1 ondersoeke beplan;

1.2 ondersoeke uitvoer en data versamel;

1.3 data evalueer en bevindinge kommunikeer.

LU 2

Konstruksie van Wetenskapkennis

Die leerder ken, interpreteer en pas wetenskaplike, tegnologiese en omgewings- kennis toe.

Dit word bewys as die leerder:

2.1 betekenisvolle inligting kan oproep;

2.2 inligting kan kategoriseer;

2.3 inligting kan interpreteer;

2.4 kennis kan toepas.

Memorandum

Aktiwiteit

Vrae:

Drywing = Arbeid(werk) Tyd

Arbeid = Krag (F) x s

Gewig = Massa x 10 =  Kg

= F x s Tyd =

2. a) 1000 Watt, m.a.w. 1 000 X Joule/sekonde

b) Die hoeveelheid kW wat per uur gelewer of verbruik word

3. Groter motors ongeveer 100kW; kleiner karre ongeveer 70kW

4. –

5. Enjin het groter drywing/vermoë om werk te verrig

6. Bereken eers totale energieverbruik (kWh):

= kW x h (uur)= 3 kW x 124 h= 372 kW

Bereken dan die koste:

= 372 x R0,35= R130,20

Aktiwiteit 2:

Toestelle se drywing per uur (min of meer):

  • Sakrekenaar 0,0006W
  • Mikrogolf 750W
  • Boor 500W
  • Radio 28W
  • Broodrooster 800W
  • Waaier 100W
  • Strykyster 1 200W
  • Stoof 1000W
  • Rekenaar 250W

Vrae:

1. Hoe groter die drywing, hoe duurder die koste om te gebruik

2. Debat

3. a) W = F x s= (75 x 10) x 320= 750 x 320= 240 000 J

Drywing = Arbeid Tyd = 240 000 J ( 20 × 60 ) = 240 000 1 200 = 200 W ( of 0,2 lW ) alignl { stack { size 12{ size 11{ ital "Drywing"= { { size 11{ ital "Arbeid"}} over { size 11{ ital "Tyd"}} } }} {} #size 11{ {}= { { size 11{"240"`"000"`J}} over { size 11{ \( "20" times "60" \) }} } } {} # size 11{ {}= { { size 11{"240"`"000"}} over { size 11{1`"200"}} } } {} #size 11{ {}="200"`W` \( ital "of"`0,2 ital "lW" \) } {} } } {}

b) W = F x s = (150 x 10) x 5= 7 500 J

Drywing = Arbeid Tyd = 7 500 J 600 s = 12 , 5 W alignl { stack { size 12{ size 11{ ital "Drywing"= { { size 11{ ital "Arbeid"}} over { size 11{ ital "Tyd"}} } }} {} #size 11{ {}= { { size 11{7`"500"`J}} over { size 11{"600"`s}} } } {} # size 11{ {}="12",5`W} {}} } {}

 Een werker se werkverrigting = 12,5  2= 6,25 W

Questions & Answers

can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
Commplementary angles
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or infinite solutions?
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The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
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Source:  OpenStax, Natuurwetenskappe graad 9. OpenStax CNX. Sep 15, 2009 Download for free at http://cnx.org/content/col11068/1.1
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