Accuracy, Precision, Significant Figures

General Physics

Accuracy

The extent to which a measured value agrees with a standard value

Parallax

Apparent shift in position when viewed at an angle

Ex. Reading graduated cylinder above or below the water line

Affects accuracy

PrecisionThe degree of exactness of a

measurementHigh precision if all numbers

are close in value Ex. 18.2 cm, 18.3 cm, 18.25

cm

Accurate, Precise, Both, or Neither

Accurate, Precise, Both, Neither

Accurate, Precise, Both, Neither

Precision and Significant Digits

The last digit of a measurement is an estimate, but is still significant

Precision of an Instrument

Reflects the number of sig. digits in a reading

All measurements made with the same instrument have same precision

Precision of an Instrument

Reading is btwn. 5.3 and 5.4 cm. What is the precision of this ruler? Hundredths place

Significant Figures

Used to report all precisely known numbers plus one estimated digit

Sig. Fig. Rules

1)Every nonzero digit is significantEx. 24.7, 237 (3 sig. figs.)

2)Zeros between nonzeros are significantEx. 7003, 40.07 (4 sig. figs)

Rules of Sig. Figs.

3) Zeros appearing in front of nonzero digits are not significant-act as placeholders, show

magnitudeEx. 0.000042, 0.34 (2 sig. figs.)

Rules of Sig. Figs

4) Zeros at the end of a number and to the right of a decimal point are significantEx. 43.60, 1.010 (4 sig. figs.)

Rules of Sig. Figs.

5)Zeros at the end of the number without a decimal point aren’t significantEx. 300 (1 sig. fig.),

27,300 (3 sig. figs.)

Sig. Fig. Shortcut

23.50

23,400

0.00560

Multiplication and Division with Sig. Figs.

Your answer can’t have more sig. figs. than the number in the calculation with the least amount of sig. figs.

Ex. Finding Area Length = 60.564278 m Width = 35.25 m Answer = 2135 m2, not 2134.8908 m2

Addition and Subtraction with Sig. Figs.

Answers can’t have more numbers to the right of the decimal point than the number with the least amount of numbers to the right of the decimal point

Ex. 22.03 + 23.1 = 45.1 Ex. 1600 + 12 + .02 = 1600