Announcements 9/8/10

Vote for TA office hour times (see email). For HW problem 4-8, you need the bulk

modulus of copper. You should get that from Chapter 12 of your book (if you don’t have that chapter, I believe there are some books chained to tables in the Tutorial Lab).

I really disliked the order that the book presented things in Chapters 20-22… so I changed the order! (The benefits of being more-or-less in charge. )

a. For Friday, we’re skipping chapter 20 and parts of chapter 21. On Monday, we’ll come back to Chapter 20, and then a week from Monday we’ll come back to Chapter 21.

22

Astronomy Club Opening Social Astronomy Club Opening Social This Friday 5-7 pmThis Friday 5-7 pm

Join the BYU Astronomical Society for Join the BYU Astronomical Society for our opening socialour opening social

This Friday from 5-7 pm in the This Friday from 5-7 pm in the Pendulum Court of the ESCPendulum Court of the ESC

We will have pizza and plan activities We will have pizza and plan activities for the upcoming semesterfor the upcoming semester

Come have fun and see what the best Come have fun and see what the best club on campus has to offerclub on campus has to offer

You don’t need to be a major, the club You don’t need to be a major, the club is open to anyone with an interest in is open to anyone with an interest in Astronomy!Astronomy!

Join our mailing list – go to Join our mailing list – go to a. http://lists.physics.byu.edu/mailman/list

info/astroclub

Questions? Contact Dr. Denise Questions? Contact Dr. Denise StephensStephens

a.a. denise_stephens@byu.edudenise_stephens@byu.edu

Benefits of Joining the club:Benefits of Joining the club:- Monthly public star parties- Monthly public star parties- Fun activities each month- Fun activities each month- Access to telescopes- Access to telescopes- Public outreach events- Public outreach events- Planetarium shows- Planetarium shows

Thought questions (review):

Water flows from the little pipe into the big pipe. Ignore any friction or height change. The volume flow rate on the right will be ______ on the left

a. greater thanb. the same asc. less than

The speed on the right will be ____ times the speed on the left.

a. 1/9b. 1/3c. 1d. 3e. 9

Thought question (review):

A ball is thrown toward you, spinning so that (as you look at it) the right side of the ball spins toward you, and the left side away. The ball will

a. “float” more than a nonspinning ballb. “sink” faster than a nonspinning ballc. curve to your leftd. curve to your right

Reading quiz (graded):

Which two temperature scales have the same sized intervals, varying only in their choice of the zero point?

a. Fahrenheit and Celsiusb. Fahrenheit and Kelvinc. Kelvin and Celsiusd. Kelvin and BTUe. Fahrenheit and Diatonic

Demos:

Liquid bulb thermometer Constant volume thermometer

Thermal expansion

What went wrong here?

Videos/Demo:

Video: Thermal expansion of wire Demo: Bimetallic strip Video: Bimetallic strip

Thought question (ungraded):

If the expansion of all of the linear dimensions of an object is proportional to ΔT, what should the expansion of the surface area of the object be proportional to?

a. ΔTb. ΔT2

c. ΔT3

d. The surface area won’t change with temperature.

e. None of the above

Thought question (ungraded)

You heat a disc with a hole in it. Will the radius of the hole get larger, smaller, or stay the same?

a. Largerb. Smallerc. Stay the same

Thought question (ungraded):

Two jars of gas: helium and neon. Both have the same volume, same pressure, same temperature. Which jar contains the greatest number of gas molecules? (The mass of a neon molecule is greater than the mass of a helium molecule.)

a. jar of heliumb. jar of neonc. same number

Ralph is confused…the book calls two different equations “the ideal gas law”: “PV = nRT”, and “PV = NkBT”. Why are they both called the ideal gas law, when only the first equation looks like what he learned in chemistry?

Quick Writing

Molecules collide like superballs (elastic) due to repulsive forces

No attractive forces Never condense into liquids or

solids Are like “frictionless surfaces”,

“massless pulleys”, “perfect fluids”, projectiles without air resistance, etc.

a. That is, don’t really exist, but are useful constructs

Ideal Gases:

Demos/Videos:

Video: “barrel crush” Demo: Liquid nitrogen balloons

Thought question:

If I heat up a balloon from 25C to 50C, about how much will its volume change?

a. By less than 10%b. By about 50%c. By a factor of 2d. By more than a factor of 2e. I’ve no idea