Physics 114: Lecture 19 Least Squares Fit to 2D Data Dale E. Gary NJIT Physics Department.
Physics 114 – Lecture 36
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Transcript of Physics 114 – Lecture 36
L36-s1,9
Physics 114 – Lecture 36• Chapter 13 Temperature and Kinetic Theory• §13.1 Atomic Theory of Matter• Democritus speculated about progressive divisions of
matter. Would a stage be reached when the matter could not be divided further without changing the nature of that matter? He thought that this would occur.
• He defined the smallest individual piece of matter to be an atom of that substance
• Mass of an atom – define mass of 12C atom to be 12.0000 unified atomic mass units
• → 1 u ≡ 1.6605 X 10-27 kg
L36-s2,9
Physics 114 – Lecture 36• Evidence for atomic theory of matter, Brown, 1827,
observed random motion of very small particles (pollen grain) suspended in liquid – known as Brownian motion
• Einstein, 1905, showed from a theoretical analysis that a typical atomic diameter ~ 10-10 m
Brownian Motion Solid Liquid Gas
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Physics 114 – Lecture 36• Study Example 13.1 – Distance between atoms• §13.2 Temperature and Thermometers• Temperature is a measure of how hot or how cold a
substance may be• Most substances expand when heated – e.g.,
expansion joints or compressible spacers are needed to accommodate this effect, bridges, concrete surfaces, …
• This expansion may be used to design a thermometer. Other attributes of a substance which changes with temperature may also be used
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Physics 114 – Lecture 36• Examples• Temperature Scales• Need two easily
reproducible temperatures
• Freezing of water –
00 C ≡ 320 F
• Boiling point of water –
1000 C ≡ 2120 F
• → Δ T (boiling point of water – freezing point of water)
= 1000 C = 1800 F - Celsius and Fahrenheit Temp Scales
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Physics 114 – Lecture 36• Conversion of Fahrenheit temperatures
to Celsius temperatures andvice versa
• Study Example 13.2• For very accurate temperature
measurement one must use aconstant volume gasthermometer – see text
32 CT5
9 FT and 32 - FT
9
5 CT 0000
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Physics 114 – Lecture 36• §13.3 Thermal Equilibrium and the Zeroth Law of
Thermodynamics• If two bodies at different temperatures are placed in
thermal contact they reach a common temperature and are said to be in thermal equilibrium
• If bodies A and B are separately in thermal equilibrium with a third body, C, then bodies A and B will be in thermal equilibrium with each other
• This statement is known as the zeroth law of therodynamics
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Physics 114 – Lecture 36• §13.4 Thermal Expansion• Linear Expansion
• ΔL = α L0 ΔT
• where α = coefficient of linear expansion
• With L = L0 + ΔL → L = L0 (1 + α ΔT)
• Units of α are (0C)-1
• For most materials α may only be considered constant over a limited range in temperature
• Study Examples 13.3, 13.4 and 13.5
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Physics 114 – Lecture 36• Volume Expansion
• ΔV = βV0 ΔT
• where β = coefficient of linear expansion
• With V = V0 + ΔV → V = V0 (1 + β ΔT)
• Again, units of β are (0C)-1
• If the material is isotropic then it is easily shown that• β ≈ 3α• Notice that the coefficient of linear expansion has no
meaning for fluids – liquids and gases – since they have no definite shape