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GraphsFor Grade 9 Physics Class

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Measuring volume of a coin byputting them into water

Number of coins Total volume/ cm3

0   15.5

1   16.5

2  17.0

3   17.9

4   18.5

5   19.5

  20.1

!   21.0

"   21.5

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What is a graph?

• A graph is a visual representationof a relationship between twovariables, – in#epen#ent variable which goes on

the !"a#is$ and

 – #epen#ent variable which goes on

the %"a#is$&•  'he graphs (a)e it easy to identify

trends in data that we have

collected&

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Graphs have these features

1$ Title – 'he co((on way to na(e your graph is to say

what your y"a#is and #"a#is are•

*ne way to say it is +%"A#is against !"A#is• Another way is +%"A#is as a function of !"A#is

2$%abelle# &'es – Write out the full name of what you have

graphed on each a#is, along with the unitsyou used&

 –  -f you are using scienti.c notation for thenu(bers, show it here also

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Graphs have these features

3$ & (ell )hosen *cale – Choose si(ple scales

• For e#a(ple/ 0 large s1uare 2 0 newton 0 3$, or 4 3, or5 3, or 06 3

 – 7ut never choose an aw)ward scale, li)e 0 s1uare2 8 3 or 3

 4. Data Plotted Correctly  – :a)e sure you are as careful as possible when

(ar)ing your points on your graph – %ou should always put little circles around each

dot, since they (ight be hard to see on the graphpaper; or use little +# for the points

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Graphs have these features

5. A Line of ‘Best Fit’ – When drawing a best .t line do not

+connect the dots&

• draw a co(pletely straight line that passesthrough as (any of your data points as possible&

• 'ry to get as (any points above the line asbelow&

 –

-f your graphed data loo)s li)e a curvedrelationship, draw a s(ooth curved linethrough your data points instead&

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Graph Practice

Plot graphs of ' against < and '4 against <

%ength+ L/

m

,erio#+ T/s T2 / s2

0$20   0.97 0.94

0$40   1.33 1.77

0$50   1.45 2.10

0$0   1.60 2.56

0$"0   1.80 3.24

1$00   2.02 4.08

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Gradient of graph• -ra#ientalso called the slope$ of a

straight line shows how steep the line is&

• -t can be calculated with the for(ula

 – =o not use the data points you plotted>

 – %ou (ust read two points fro( the best .tline&

 – Give the gradient a unit based on the unitsof the a#es rise over run$

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