Physics 203204

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Physics 213 Fluids Thermal Physics Lecturer
John Huckans Office hours Wednesdays 12-2pm,
150A Davey Web Page class.phys.psu.edu/p213su

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Teaching assistance

• Rec TA - David Simpson, dbs200_at_psu.edu
• Rec TA - Casey Tomlin, ctt121_at_psu.edu
• Lab TA - Christian Cruz-Santiago, czc146_at_psu.edu
• Lab TA - Shan Gao, sxg324_at_psu.edu
• Course administrator John Hopkins
• jxh22_at_psu.edu
• 123 Osmond Lab

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Physics 213

• Calculus-based study of the basic concepts of
  fluids and sound, heat, kinetic theory, and
  entropy.
• Prerequisite MATH 140 , PHYS 211
• Concurrent MATH 141
• Textbook Fundamentals of Physics, Halliday
  Resnick and Walker, 8th Edition, Vol. 1
• Attendant lab manual and WebAssign card

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Course information

• Lecture notes available on-line by 8 a.m. day of
  the lecture
• Must be on time for laboratories if more than
  10 minutes late, no credit for lab
• Recitations are an opportunity to clarify
  concepts and ask homework questions
• Homeworks due Thursdays by 5pm no exceptions

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Physics 213 four week schedule
Intro lecture
Lecture 1
Lab 1 (drop/add)
Recitation
Lecture 2
Midterm June 26
Lab 2
Recitation Midterm prep
Lecture 3
Recitation
Lecture 5
No class July 3
Lab 3
Recitation
Lecture 4
Final July 10
Recitation Final prep
Lecture 6
Recitation
Lab 4
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Chapter 12 Section 12-7 Elasticity
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Elasticity

• Up to now (in Phys 211) we have assumed that
  rigid bodies cannot be deformed.
• In practice, given a strong enough force
  everything can be deformed.

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Stress and Strain
Stress external force per unit area acting on
the object, F/A
Dimension Force/Area, e.g. N/m2
Strain fractional change in size of the object,
DL /L or DA/A or DV/V
Dimensionless
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Elastic, Deformation, Rupture
For small stress, rigid bodies are elastic
strain ? stress
stress modulus of elasticity strain
When stress is larger than the yield strength Sy,
rigid bodies are permanently deformed.
When stress is larger than the ultimate strength
Su, rigid bodies rupture.
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Tensile and Compressive Stresses
Strain and stress in the same direction.
Tensile stretch Compressive squeeze.
stress modulus of elasticity strain
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Shearing Stress
Strain and stress also in the same direction.
stress modulus of elasticity strain
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Hydraulic Stress
Stress is the pressure by a fluid, p.
strain modulus of elasticity stress
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• HRW 12-64 (7th ed.) A mine elevator is supported
  by a single steel cable 2.5 cm in diameter. The
  total mass of the elevator cage plus occupants
  is 670 kg. By how much does the cable stretch
  when the elevator is (a) at the surface, 12 m
  below the elevator motor, and (b) at the bottom
  of the shaft which is 350 m deep? (Neglect the
  mass of the cable.)

(a) For L1 12 m
(b) For L2 350 m 12 m
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• HRW 12-39 (7th ed.), 13.39P (6th ed.) In the
  figure, a 103 kg uniform log hangs by two steel
  wires, A and B, both of radius 1.20 mm.
  Initially, wire A was 2.50 m long and 2.00 mm
  shorter than wire B. The log is now horizontal.
  What forces are exerted on it by (a) wire A, and
  (b) wire B? (c) What is the ratio of dA/dB?

(a) Since the log is not moving FA FB mg 0
Since the log is horizontal LA DLA LB DLB
LA l DLB, DLA DLB l, where l 2 mm is
the original difference in lengths between A and
B.
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HRW 12-39 (7th ed.), 13.39P (6th ed.) In the
figure, a 103 kg uniform log hangs by two steel
wires, A and B, both of radius 1.20 mm.
Initially, wire A was 2.50 m long and 2.00 mm
shorter than wire B. The log is now horizontal.
What forces are exerted on it by (a) wire A, and
(b) wire B? (c) What is the ratio of dA/dB?
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HRW 12-39 (7th ed.), 13.39P (6th ed.) In the
figure, a 103 kg uniform log hangs by two steel
wires, A and B, both of radius 1.20 mm.
Initially, wire A was 2.50 m long and 2.00 mm
shorter than wire B. The log is now horizontal.
What forces are exerted on it by (a) wire A, and
(b) wire B? (c) What is the ratio of dA/dB?