Lesson 2: Measurement (Gen-Physics 1).pptx

Lesson about measurement in general physics

1. LESSON 2: MEASUREMENTS
OBJECTIVES OF THE DAY
«| will be able to describe the need
for measurement;

«| will be able to carry out simple
measurements of length, volume,
and mass; and

«| will be able to differentiate the

accuracy and the precision of a
measurement

2. Keywords for the concepts to be learned; N

a.Measurements

b.Unit of Measurements
c.Accuracy Be
d.Precision WHAT GETS MEA SURED
e.Significant figures PETS IMPROVED

f. Errors

3. Measurements

*The study of matter requires a certain
degree of measurements, a process of
determining the extent of the dimensions,
quantity, or extent of something.

* Questions such as “How much
long...?” and “How many...?” simple
cannot be answered without resorting to
measurement.

Q1. Can you cite some situations in daily life
where a measurement is important?

4. Units of Measurements

Table 1. SI base units
« The most convenient system SI base unit
of units is the International Base quantity Name Symbol
System of Units (SI).

kilogram Kg

* This system is the modern SIEHE currant ampere A
versions of metric system.

amount of substance mole mol

5. Units of Measurements Q

The name of the fractional parts and the multiples of the base units are
constructed by adding prefixes. These prefixes, shown in table, indicate
the size of the unit relative to the base unit.

1 yottametre = 1 = 000 000 000 000 == 000 000 metres Sepullion

1 zettametre = 1 000 000 000 000 000 000 000 metres ‘Sextillion

ametre = 1 000 000 009 000 000 000 metres quintillion

1 petametre = ı 000 000 000 000 000 metres quadrillion

1 terametre = 1 000 000 000 000 metres tation

1 gigametre = 1 000 000 000 metres billion.

1 megametre = 1 000 000 metres = mio

1 micrometre = 0.000 001 metres

1 nanometre = 0.000 000 001 metres

1 picometre = 0.000 000 000 001 metres

2 femtometre = 0.000 000 009 000 001 metres

1 atrometre = 0.000 000 009 000 000 001 metres = Quintllionen

i zeptometre = 0.000 000 000 000 000 000 001 metres z sextilionth

1 yoctometre = 0 000 000 000 000 000 000 000 001 metres _ Septillionth

6. Uncertainty in Measurements Q

« A measured quantity contains some digits that are exactly
known and one digit that is estimated. The estimated digit
produces uncertainty in measurements.

7. Random Error and Systematic Error Q

* RANDOM ERROR (indeterminate error) is the uncertainty
that arises from a scale reading which results from the
uncontrolled variables in the measurement.

* It causes one measurement to differ slightly from the next. It
comes from unpredictable changes during an experiment.

Examples

a. When weighing yourself on a scale, you position yourself
slightly different each time.

b. Measuring your height is affected by minor posture changes.

8. Random Error and Systematic Error Q

+ SYSTEMATIC ERROR (determinate error) is the uncertainty
that may come from a flaw in the equipment used or design of
an experiment. These error are usually caused by measuring
instruments that are incorrect calibrated or are used
incorrect.

« Examples

a. Aworn out instrument

b. An incorrectly calibrated or tared instrument

c. Aperson consistently take an incorrect measurements

a

9. Precision and Accuracy

Q

« Precision is the consistency of a result. If you measure a
quantity several times and the values agrees closely with one
another, then your measurement is precise.; however, if the
values varied widely, then it is imprecise.

+ Accuracy is determined when a certain quantitative value is
relatively close to the “true value”

10. Activity 7 Q

Precision versus Accuracy:
Look at each target and decide whether the "hits" are accurate, precise, both accurate
and precise, or neither accurate nor precise: (Note: An accurate “hit” is a bulls eye!)

11. Scientific Notation Q

+ It is a simple way to write or keep track of very large or very
small numbers without having to deal with a lot of zeros.

« It provides a convenient way of recording results and doing
calculations.

Scientific Notation

2.5 x 10°%,
Exponent

A
Coefficient

12. Scientific Notation

To convert to scientific notation:

Biponient Rues „Becmalpeint „ Decimal point, Exponent aces din

moves right
Examples:

156000. = 1.56 x 10* 0.0000053 = 5.3 x 105

Move decimal point 5 places left, Move decimal point 6 places right,
exponent goes up by 5 exponent goes down by 6

13. Activity 8

1. 0.012345698632

2. 1 230 945

3. 87 576 788 432 234 543
4. 0.0600789653

5. 11 987

14. Significant Figures Q

+ Significant figures are the digits in any measurement that
are known certainty with an additional one digit which is

j RULES MEASURED NUMBERS NUMBER OF SIGNIFICANT

1. All nonzero digits are significant.

247 3
2. Zeroes between nonzero digits
are significant. 20303 5
3. Zeroes to the left of the first
nonzero digits are NOT significant 0.0200 3

15. Significant Figures

RULES MEASURED NUMBERS
4. If the number is less than 1, then
only the zeros at the end of the 0.003560 4
number and the zero between

5. If the number is greater than 1,
then all the zeros written to the right
of the decimal point are significant. 35600.00 Li

16. Activity 9

Give the number of significant figures for each of the following measurements.

1.2 365 mm
2. 309 cm

3. 5.030 g/mL
4. 0.0670 g

17. Activity 10

Give the number of significant figures for each of the following measurements.

1. 0.476 kg
2. 89.7808 ft
3. 0.430 mg
4.60.0 min

18. Rules for Significant Figures in Fundamental Operations []

+ In addition and subtraction, the answer must have the same
number of decimal places as the measured number with the
least number of decimal places.

+ In multiplication and division, the answer must have the
same number of significant figures as the measured number
with the lowest number of significant figures.

19. Rules in Rounding Off

« Oftentimes, the answers to
computations contain too many
insignificant digits. Hence it
becomes necessary to round off
numbers to attain the insignificant
figures. Rounding off, therefore, is
the process of removing,
insignificant digits from calculated
number.

‚00670054

|

006701

Neghoonng
ans

20. Rules in Rounding Off Q
+ The following rules should be applied to round off values to
the correct number of digits.

1. For a series of calculations, carry extra digits through to the
final result, then round off.

2. If the first digit to be deleted is....
a. 5 or greater, the last retained figure is increased by one
b. 4 or less, the last retained figure is retained.

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