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Phy 2053 Announcements 1.

„ „ „ „ „ „ Exam 2 is coming soon!!

Thursday, April 2, 8:20 – 10:10 pm „ Material from Chapters 5-8 of Serway/Vuille Only the sections we covered in class „ „ 20 questions, multiple choice Very much like the first exam There is only one correct answer to the question “In order to receive credit for this problem, you must correctly code (“bubble in”) your UFID and your 5-digit test number…” Æ I have correctly bubbled my UFID number and 5-digit test code.

„ Please get there

at least

10 minutes early, and preferably 20 minutes New protocols - stay in your seat until your exam is collected. Raise your hands; proctors will come to collect it. If you want to avoid the long wait at the end, either (a) come early and sit at the front or (b) finish early Please circle your answer on the exam More Phy 2053 Announcements „ „ „ „ „ „ „ „ „ „ „ Room assignments for Exam 2 BRY130: A-ELU FLG220: EMM-HER FLG230: HEW-LAI FLG260: LAM-MON FLG270: MOO-P LIT121: R-SAW MAEB211:SCH-T MAT18: U-Z You be allowed one

handwritten

(both sides), 8 ½” x 11” paper In class review, Tuesday, March 31 formula sheet Even More Phy 2053 Announcements „ „ „ „ Make-up exam for students missing Exams 1 and 2 will be held Wednesday, April 22 from 7:20 – 9:10 pm Room to be announced later „

If you need to take a make-up because of a legitimate excuse, please send Prof. Chan and I an e-mail as soon as possible

HW Assignment 9 due two weeks from yesterday, Wednesday, March 8 But, you should do the problems from Ch 8 before the test!

Rotational Kinetic Energy

Equivalent to KE =

KE

= 1 2 1 2

I

ω

m

v 2 2 (

KE t

+ Conservation of Mechanical Energy

KE r

+

PE g

+

PE

= (

KE t

+

KE r

+

PE g

+

PE

Work-Energy Theorem: W nc = Δ KE t + Δ KE R + Δ PE Example: Problem 8-44, p 262 Four objects – a hoop, a solid cylinder, a solid sphere, and a thin, spherical shell – each have a mass of 4.8 kg and a radius of 0.23 m. (a) Find the moment of inertia for each object as it rotates about the axes shown in Table 8.1. (b) Suppose each object rolls down a ramp without slipping. Rank the translational speed of each object from highest to lowest. (c) Rank the objects’ rotational kinetic energy from highest to lowest as the objects roll down the ramp. θ http://www.photoshopsupport.com/photoshop-blog /05/10/11-liquid-sculpture.html

http://p25ext.lanl.gov/~hubert/aerogel/

Chapter 9 Solids and Fluids

www.pbs.org/wgbh/nova/volcano/anat_02.html

1

„

States of Matter

Solid „ „ Atoms close together Fixed positions „ Electrostatic forces „ Quantum mechanics!

I - crystalline „ Liquid „ „ No long range order (usually) at higher Temperatures „ „ Gas „ Molecules are in constant random motion „ „ Molecules exert weak forces on each other Average separation is large compared to the size of the molecules Plasma „ Gas heated to a very high temperature „ Many of the electrons are freed from the nucleus II - amorphous

Strength of materials States of matter – what we don’t know

What the universe is made of: ?

?

We know about this edelweiss.in2p3.fr/Presentation/index.php

Elastic Properties of Solids

„ „ „

Stress

is the force per unit area causing the deformation

Strain

is a measure of the amount of deformation The

elastic modulus

of proportionality between stress and strain is the constant „ „ For sufficiently small stresses, the stress is directly proportional to the strain The constant of proportionality depends on the material being deformed and the nature of the deformation 2

Quantitative characterization of mechanical properties of materials Elastic behavior: Hooke’s Law

Why is

stress

defined as force per unit area (F/A) ??

What is

strain

?

http://www.youtube.com/watch?v=3UZuPayyAnM

Young’s Modulus: Elasticity in Length

A L 0 Δ L F

Stress = F/A Strain =

Δ

L/L

0

Young’s Modulus:

F A

=

Y

Δ

L L o

Stress = Y x Strain

or

Stress Strain

=

Y

3

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