Transcript IB Graphing - Red Hook Central School Dst

IB Graphing
Error Bars
• When measurement expressed with absolute
uncertainty - graph with error bars.
• Bar is sketched as vertical and horizontal
lines beginning at data point ending in
horizontal line or cap.
• Bars are scaled to the graph axis.
distance (m) ±0.5
Error bars
time (s)±0.01*
Error bars too small to show at this scale
Some error bars are different lengths why?
Different instruments
Calculated deviation from mean for each.
Usually give graphical data display because:
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See relationship btw variables.
See outliers from data.
Show math relationship.
Finding constants.
How to graph
• Graph axis independent (x) / dependent (y). Not
always.
• Scale – large.
• Slope points – far apart.
• Plot dot circled or dot w/bars.
• Line or curve of best fit by hand. Can buy shape to
help fit curves. Should touch error bars.
• Best fit straight line may or may not pass through
origin.
• Transform curves.
• Calculate slope & slope uncertainty for linear.
Hooke’s Law data
Make graph with error bars
Force ± 5 N
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Stretch ± 0.2 cm 3.0
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4.4 6.2 7.5
9.1
Force ± 5 N
Graph with error bars & fit line
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Stretch ±2 cm
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Graph Analysis
Force N
• Linear y = mx + b
test
• Since slope is constant, y/x = k any 2 points
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• What graph is this?
• Y = -kx.
• This is a linear graph!
Inverse hyperbolic
• Y = k/x
yx = k
• Transform graph by plotting y against 1/x
to get linear.
Parabolic
• Y = kx2.
y/x2 = k
• Or transform graph y against x2 make it linear
• What will the slope be?
Craters DBQ
Strobe Ball Drop
• Kerr activity pendulum