MEASUREMENT LIMITATIONSMEASUREMENT LIMITATIONS

MEASUREMENT LIMITATIONS

• 1) ACCURACY–HOW CLOSE THE MEASUREMENT

IS TO AN ACTUAL OR ACCEPTED VALUE–DEPENDS ON YOU –GETS BETTER WITH PRACTICE

% ERROR• ALLOWS YOU TO EVALUATE THE

ACCURACY OF YOUR DATA• EQUATION:

• 2) PRECISION–AGREEMENT OF A SET OF VALUES –REPRODUCIBILITY OF DATA–MEASUREMENTS CAN ONLY BE

AS PRECISE AS YOUR MEASURING TOOL (BASED ON HOW GRADUATED IT IS)

1. 2.

3. 4.

SIGNIFICANT FIGURES (DIGITS)

• INDICATES PRECISION OF AN INDICATES PRECISION OF AN INSTRUMENT INSTRUMENT • DEFINITION: ALL CERTAIN VALUES ALL CERTAIN VALUES

(FROM GRADUATIONS ON TOOL) AND ONE ESTIMATED OR AND ONE ESTIMATED OR UNCERTAIN VALUEUNCERTAIN VALUE (SPACE BETWEEN LAST GRADUATIONS)

READING A METER STICK FOR PRECISION

• SEE SIDE BOARD. COPY DOWN INFORMATION AS TEACHER EXPLAINS.

RULES OF SIGNIFICANT DIGITS

• 1)ALL NONZERO DIGITS ARE SIGNIFICANT–EX: 275.68 g = 5 SIG FIGS

• 2) ZEROES BETWEEN 2 NONZERO DIGITS ARE SIGNIFICANT–EX: 1205 mL = 4 SIG FIGS

• 3) ALL ZEROES AFTER THE LAST NON-ZERO DIGIT IN A NUMBER WITH AN UNDERSTOOD DECIMAL ARE NOT SIGNIFICANT. (THEY ARE PLACEHOLDERS)–EX: 104 000 m = 3 SIG FIGS*THE NUMBER HAS BEEN

ROUNDED

• IF YOU WANT TO MAKE ZEROES SIGNIFICANT IN A NUMBER WITH AN UNDERSTOOD DECIMAL, PLACE A LINE OVER THE LAST ZERO THAT IS SIGNIFICANT.–EX: 104 000 m = 5 SIG FIGS

• 4) ALL ZEROES IN FRONT OF THE 1ST NON-ZERO DIGIT IN A NUMBER LESS THAN 1 ARE NOT SIGNIFICANT. (THEY ARE PLACEHOLDERS)–EX: 0.00589 g = 3 SIG. FIGS*THINK OF THESE NUMBERS AS

FRACTIONS; ONLY SIG FIGS GO IN THE NUMERATOR

• 5) ALL ZEROES AFTER A DECIMAL AND AFTER THE 1ST NON-ZERO DIGIT ARE SIGNIFICANT–EX: 0.07050 L = 4 SIG FIGS 30.00 mg = 4 SIG FIGS*BE CAREFUL BECAUSE YOUR

CALCULATOR REMOVES THE ZEROES AT THE END OF NUMBERS

• 6) ITEM COUNTS HAVE UNLIMITED SIG. FIGS.–EX: 10 APPLES → UNLIMITED 60 s = 1 min → UNLIMITED

PRACTICE PROBLEMS• COPY AND ANSWER IN YOUR

NOTEBOOK. PUT A BOX AROUND THE SIG FIGS.–1. 5600 m 2. 0.0078 L–3. 30024 g 4. 780.0 ng–5. 34.078 mL 6. 0.002008 km–7. 1000 PIES 8. 50.091 dL