Unit B Energy Flow
Skills Development
Graphing and
Name: ____________________________________
Date: ___________________Block: _________
Measurements
Taking Measurements
All measurements are subject to uncertainties. All instruments used are influenced by
external circumstances, and the person making the reading may affect the
accuracy of a measurement.
A measurement is accurate when it is close to the accepted value and it is limited by the
quality of the instrument used to make it. A measurement is more precise when it contains a
large number of digits. e.g. 120 cm 119.9973 cm
The precision of an instrument is limited by the smallest division on the measurement scale.
When you read any measuring device, you always record the measurement by reading the
smallest division on the scale and then “guessing at” or estimating, the tenth of the smallest
division.
ESTIMATES CREATE UNCERTAINTY!
Significant Digits
Significant digits are all those digits obtained from a properly-taken measurement: _________
_________________________________________________________________________________________.
Exact numbers have an infinite number of significant digits, because they do not involve an
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Unit B Energy Flow
Skills Development
estimated measurement. Exact numbers are:
a) numbers that are _________
e.g.
1000 m = 1 km
1 dozen = 12
b) numbers that results from _________________
e.g. 32 students
150 books
To determine that number of significant digits in a measurement, count from left to right,
beginning with the first digit that is not zero.
For each of the following measured values, indicate the number of significant digits.
When we perform calculations with measured values, the result contains some significant
figures and some that are not because the arithmetic was performed with uncertain
numbers.
Our answer can NEVER be more precise than the least precise value we used in our
calculations.
Adding and Subtracting
When adding or subtracting, round off the answer to the __________________________________
_________________________________________________________________________________________.
Multiplying and Dividing
When multiplying or dividing round off the answer to the __________________________________
_________________________________________________________________________________________.
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When doing a series of calculations to arrive at an answer, ________________________________.
Only round your final answer. If possible, keep the significant digits in your calculator.
Graphing Skills
Independent Variable
The independent variable is also called the
manipulated variable.
______________________________________________________
______________________________________________________
Dependent Variable
The dependent variable is also called the responding
variable.
______________________________________________________
______________________________________________________
Lines of Best Fit
Recall that taking measurements as part of any experiment results in some unavoidable builtin error or uncertainty.
To minimize the effect measurement errors on experimental results we often repeat the same
measurement over and over in multiple trials.
Another common averaging technique is to plot the data on a graph, and draw a line of
best fit.
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__________________________________________________________________________________________
_________________________________________________________________________________________.
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For example, to determine the density of a liquid, a student measures the mass of various
volumes of the liquid.
Defining Slope
The slope of a line is a measure of how steep the line is.
When choosing the two points to substitute into the slope formula, you must NEVER choose
values from the data table. Only read the points from the line of best fit.
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Unit B Energy Flow
Skills Development
Lines with a positive slope rise to the right.
Lines with a negative slope fall to the right.
Horizontal lines have a slope of zero.
Vertical lines have an infinite slope.
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