About myself

Office hours: by appointment

• Dr. Soeren Prell– Office: A417 Zaffarano– Phone: 294-3853– E-mail: prell@iastate.edu

• Courses taught at ISU (since 2002)– Introduction to Classical Physics I + II– Modern Physics Lab – Quantum Mechanics I + II

• Research– Experimental elementary particle physics

at the Large Hadron Collider (LHC)

• Hobby– Judo coach at Cyclone Martial Arts Club

The Physics 222 Instructor Team• Lecturers:

– Soeren Prell

• Course secretary– Deb Schmidt

• Lab supervisor– Paula Herrera

• Recitation and Lab Teaching Assistants:– Meijian Li, Carlos Vergel Infante, Kamal Raj Joshi,

Andres Garcia, Kevin Marasinghe Chirag Vaswani, Bob Mayer, Ragavi Pala Janardhan, Krishna Leela Rajana

The syllabus• Linked from Phys 222 course web page (under Course Info)

– http://course.physastro.iastate.edu/phys222/

• Lecturer contact information • Textbook and other course material

– Incl. for online homework• Course schedule

– Lectures, recitations, hw assignment due dates (online hw and reading), quizzes, exams, etc.

• Grading policy

First homework assignment: read the syllabus carefully!

Exams

• 2 mid-semester exams– Evening exams at

• Final exam

Wednesday, February 18 8:15 pm – 10:15 pmWednesday, April 1 8:15 pm – 10:15 pm

May 4 – 8 time and day TBA, 120 minutes

Make no other plans for these evenings !

Recitations

• Each Tuesday (50 minutes)

– Worksheets (40 minutes)• Hands-on, interactive learning

– Quizzes (10 minutes)

Labs• 14 two-hour labs• Each section meets every week• Prelab must be completed before corresponding lab• Check lab schedule for dates and time of your

session• Detailed lab info on Blackboard

– For questions regarding labs, e-mail Paula Herrera (siklody@iastate.edu).

Questions based on material covered in recitations and labs will be on the exams !

Student Assistance

• Physics 222 help room (=TA office hours)• Lecturer office hours• Physics 222 course web page and info on

Blackboard• Discussion board on Blackboard• SI session for Physics 222

How to succeed in Physics 222Physics can only be learned by doing it

(just like swimming or juggling)

• Lectures– Prepare for lecture

• Read the indicated assignments before class

– Attend actively• Ask questions, participate in interactive problems

• Homework– Do all problems– Review the HW solutions– Understand and learn from your mistakes

Lectures

• Turn off your cell phone in lecture• No laptops in lecture• Bring your clicker

– Register it on the Physics 222 Blackboard page• No need to bring your textbook• Note taking

– Lecture notes will be posted on the course web page before each lecture

Lecture 1Fluids: density, pressure,

Pascal’s principle.Water tower Hydraulic

press

Pascal’s vasesBarometer

What is a fluid?

Fluids are “substances that flow”…. “substances that take the shape of the container”Fluids are “substances that flow”…. “substances that take the shape of the container”

Atoms and molecules must be free to move. No long range correlation between positions (e.g., not a crystal).

Atoms and molecules must be free to move. No long range correlation between positions (e.g., not a crystal).

Gas or liquid… or granular materials (like sand)Gas or liquid… or granular materials (like sand)

Density, pressure

Vm

Density:

Fp

APressure:

Units: Pascal (Pa) = 1 N/m2

psi (pounds per square inch)

atmosphere 1 atm = 1.013 × 105 Pa

bar 1 bar = 105 Pa

Units: Pascal (Pa) = 1 N/m2

psi (pounds per square inch)

atmosphere 1 atm = 1.013 × 105 Pa

bar 1 bar = 105 Pa

Pure water: 1000 kg/m3Pure water: 1000 kg/m3

Atmospheric pressure

DEMO: Piston and weight

The atmosphere of Earth is a fluid, so every object in air is subject to some pressure.The atmosphere of Earth is a fluid, so every object in air is subject to some pressure.

At the surface of the Earth, the pressure is

patm ~ 1.013 x 105 Pa = 1 atm

At the surface of the Earth, the pressure is

patm ~ 1.013 x 105 Pa = 1 atm

Area of a hand ~ 200 cm2 = 0.02 m2

Area of a hand ~ 200 cm2 = 0.02 m2

atm ~2000 N on your hand due to air!F p A

Pressure vs. depth

Fbottom

Ftop

mg

Imaginary box of fluid with density ρ with bases of area A

and height h

Imaginary box of fluid with density ρ with bases of area A

and height h

bottom/ top

bottom/ top

FP

A

bottom topp p gh

m Ah

hNet force must be zero!Net force must be zero!

bottom topF F mg

DEMO: Plastic tube with cover

5bottom top

3 3 2

Example: How deep under water is = 2 atm?

1.01 10 Pa10.3 m

10 kg/ m 9.81 m/ s

( . ., 1 atm is produced by a 10.3 m high column of water)

p

p ph

g

i e

Fluid in an open container

Pressure is the same at a given depth, independently of the container.

p(y)

y

Fluid level is the same everywhere in a connected container (assuming no surface forces) •

A•B

If liquid height was higher

above A than above B

If liquid height was higher

above A than above B

pA > pB pA > pB Net forceNet force Net flowNet flow This is not

equilibrium!

This is not equilibriu

m!

DEMO: Pascal’s vases

Water towers

Water towers are a common sight in the Midwest… because it’s so flat!

Water towers are a common sight in the Midwest… because it’s so flat!

hh

house atm waterp p hg

So physics sucks, but how much?

Your physics professor sucks on a long tube that rises out of a bucket of water. He can get the liquid to rise 5.5 m (vertically). What is the pressure in his mouth at this moment?

Your physics professor sucks on a long tube that rises out of a bucket of water. He can get the liquid to rise 5.5 m (vertically). What is the pressure in his mouth at this moment?

A. 1 atm

B. 0.67 atm

C. 0.57 atm

D. 0.46 atm

E. 0 atm

A. 1 atm

B. 0.67 atm

C. 0.57 atm

D. 0.46 atm

E. 0 atm

DEMO: Sucking through a hose

water atmmouth

atm watermouth

5 3 3 2 10 Pa 10 kg/ m 9.8 m/ s 5.5 m

46100 Pa 0.46 atm

p gh p

p p gh

hh

x Ax A

x Bx B

Pascal’s principle

Any change in the pressure applied to an enclosed fluid is transmitted to every portion of the fluid and

to the walls of the containing vessel.

Pascal’s Principle is most often applied to incompressible fluids (liquids):

Increasing p at any depth (including the surface) gives the same increase in p at any other depth

Pascal’s Principle is most often applied to incompressible fluids (liquids):

Increasing p at any depth (including the surface) gives the same increase in p at any other depth

Hydraulic chamber

F2 can be very large…

F2 can be very large…

No energy is lost:No energy is lost:

Measuring pressure with fluids

Barometer Measures absolute pressure Top of tube evacuated (p = 0) Bottom of tube submerged into pool of

mercury open to sample (p) Pressure dependence on depth:

Hg

ph

g

Barometer

Sample at p

Sample at p

hh

Vacuum p0 =

0

Vacuum p0 =

0

pp patmpatm

∆h∆h

p

Δh

p0

Manometer Measures gauge pressure: pressure relative to

a normalization pressure. Pressure dependence on depth:

A unit for pressure

760 mm Hg = 760 torr = 1/760 atm