Aim: How do we record measurements?

Do Now:

Record the measurements of A, B, and C

0 A 1 2 B C 3

Rule: State the digits that you know for certain and estimate one extra digit. This shows the precision of your measuring instrument.

Acceptable answers to the do now:

A – 0.2

0.3

0.4

B – 2.26

2.27

2.28

2.29

C – 2.80

Certain digit

Estimated digit

Certain digits

Certain digits

Estimated digit

Estimated digit

B and C are more precise measurements

Worksheet on measurements

Take out a ruler

12.5111.3013.26

13.9410.31 11.72

14.3412.97

9.7112.01

-2.4 37.9 8.1 86.5 -10.5 34.6

4.50

45.0

7.40

74.0

3.50

35.0

4.15

41.5

9.25

92.5

8.70

87.0

1.35

13.5

Uncertainties in Measurements

In devices:

•A metal ruler’s length can change with changes in temperature

•Electric devices can be affected by magnetic fields near them

With People:

•Reading an instrument from an angle (not at eye level) could result in incorrect

readings

Parallax – the apparent shift in the position of an object when it is viewed from various angles

Precision – the degree of exactness to which a measurement can be reproduced

- limited to the smallest division on the scale of the instrument

Accuracy – how well the result agrees with an accepted value

Describe the dart player’s throws:

x

x

x

xxx

x xx

Not precise

Not accurate

Precise

Not accurate

Precise

Accurate

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