Physics 1710 Chapter 1 Measurement

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Physics 1710Chapter 1 Measurement

• 1 Lesson
• Time, measured in seconds
• Length, measured in meters
• Mass, measured in kilograms.
• Prefixes scale units to convenient size.
• Density is mass per unit volume. kg/m3
• Avogadros number is the number of atoms
• in a mole of an element.

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Physics 1710Chapter 1 Measurement
Mattesons Dicta Numbers 1 2 1. Physics is
that branch of science concerned with the
interaction of matter-energy in space-time. 2.
The physical universe consists of only matter and
energy and the vacuum.
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Physics 1710Chapter 1 Measurement
Measurement is the quantitative comparison of a
physical parameter to a standard unit. Accuracy
is the difference of a measurement from the
(unknown) true value. Precision is the fineness
of the division of the scale used to compare to
the standard unit.
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Physics 1710Chapter 1 Measurement

• 80/20Precision is the fineness of a measurement.
• 80/20Accuracy is the correspondence of a
  measurement to an (unknown) true value.

Measurement
Less precise
Standard
Less accurate
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Physics 1710Chapter 1 Measurement
Significant figures What numbers one writes down
reveals ones knowledge (and ignorance) of the
actual true (but unknown) value. Example 2.
2.0 2.01 2.0085 2.00852 represent the
values of a measurement at various levels of
precision.
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Physics 1710Chapter 1 Measurement

• Rules for Computing with Significant Figures
• When multiplying (or dividing) numbers, round
  result to same number of significant figures as
  the factor with least number of significant
  figures.
• When adding (or subtracting), first round to same
  place as contribution with the least number of
  significant figures, then compute.

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Physics 1710Chapter 1 Measurement

• Scientific Notation
• Big Numbers 1.234567 x 10 3 1234.567
• Small Numbers 1.234567 x 10 2 0.01234567

Know your calculator Enter 1.234567 EXP or
EE 03 1.234567 03 Enter 1.234567 EXP 03
/- 1.234567-03
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Physics 1710Chapter 1 Measurement

• Time Standard second s
• (1/60)(1/60)(1/24) 1/86,400 mean solar day
• 9,192,631,770 times the period of vibration of
  a cesium-133 atomic clock.
• Time Demonstration

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Physics 1710Chapter 1 Measurement

• Length standard meter m
• Meter defined in 1795, by French Republic.
• 1/107 quadrant of Earth.
• Distance light travels in 1/299,792,458 sec
• Meter Demonstration

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Physics 1710Chapter 1 Measurement

• Derived Units of area and volume
• area 100 m x 100 m 10 4 m 2 hectare ha,
  
• volume m x m x m m 3 1000 liter 1000 l
• e.g. 1000 cm 3 1 liter

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Physics 1710Chapter 1 Measurement

• Derived Units of area and volume
• 1 acre 4 046.85642 m2 0.4046 ha
• volume m x m x m m 3 1000 liter 1000 l
• e.g. 1000 cm 3 1 liter
• 1 US gallon 3.7854118 liters 3.8 l

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Physics 1710Chapter 1 Measurement

• Mass Standard kilogram kg
• kilo 1000
• 1 kg is the mass of approximately 1/1000 m3
  of water
• Mass is a fundamental property of all matter.
• Each atom has a mass of 1.66 x 10-27 kg times
  its atomic mass number

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Physics 1710Chapter 1 Measurement

• Mass Standard kilogram kg
• 1 kg weighs on earth about 2.2 pounds.

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Physics 1710Chapter 1 Measurement

• Amedo Avogadro
• (1776-1856)
• Italian Physicist
• Proposed Avogadros Law (1811)

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Physics 1710Chapter 1 Measurement
Avogadros Number NA 6.0221367(28) x 10 23
atoms/mole Atomic mass unit u u 1.660 540
2(10) x 10 27kg NA u 1.00 x 10 3 kg 1.00
gram NA is the number of atoms in one gram
molecular weight of an element.
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Physics 1710Chapter 1 Measurement
Practice How much does a 5 US Gal can of water
weigh?
Density of water 1.0 kg/l M ? V (1.0 kg/l
)(5 gal x 3.8 l/gal) 19. kg W 2.2 lbs/kg x
19. kg 42. lbs
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Physics 1710Chapter 1 Measurement

• Summary
• Time, measured in seconds
• Length, measured in meters
• Mass, measured in kilograms.
• Prefixes scale units to convenient size. k
  1000, M 1 000 000 c 1/100, m 1/1000, µ
  1/1 000 000
• Density is mass per unit volume. ? m/V kg/m3
  
• Avogadros number is the number of atoms
• in a mole of an element. 6.022 x1023 atom/mole