Fun, and don't forget about quiz next class.

http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/

http://www.youtube.com/watch?v=0fKBhvDjuy0

http://www.atlasoftheuniverse.com/

http://sunshine.chpc.utah.edu/labs/cosmic_zoom/cosmic_zoom2.swf

http://physics.weber.edu/schroeder/software/zoomer.html

http://htwins.net/scale2/
WAY COOL

Again, worth seeing:

http://www.essex1.com/people/speer/model.html

http://rense.com/general72/size.htm

Also....

Plan on a quiz to take place during the class after next - that would be next Monday.

Wave work.

Work if you have time:

1.  What are the units of:  amplitude, frequency, wavelength, period, speed/velocity?

2.  A pendulum takes 0.25 seconds to complete one swing.
a.  How many swings per second does it make?
b.  What is this amount called?
c.  What is the length of this pendulum?

3.  A mass on a spring oscillates 3 times per second.  What is the time between oscillations?

4.  Consider a basic (sine) wave.  Identify the important parts of the wave:  crest, trough, wavelength, amplitude.

5.  Four complete waves pass a point every 10 seconds. 
a.  What is the period of one wave?
b.  If the four complete waves have a total length of 16-m, what is the wavelength of one wave?
c.  What is the speed (v) of this wave?

5.  The speed of sound is approximately 345 m/s.  What is the wavelength of a 440-Hz sound wave?  This note is a concert A, by the way.

Play.

2 things for HW:

a.  Play around with this applet:

http://phet.colorado.edu/sims/wave-on-a-string/wave-on-a-string_en.html

Set the damping to 0, to get a "no friction" situation - that's not totally realistic, but it makes it easier to see things.  Make notes that are helpful as you play around with the applet.

More details (and other applets) are here, if you're interested.

http://phet.colorado.edu/en/simulation/wave-on-a-string


b.  The phenomenon of the pendulum is described as undergoing "simple harmonic motion."  What do you suppose might be a connection between such motion and the motion of waves?  Think about this and write about it, if you can.  Furthermore, what is "wavelike" about a pendulum?

Enjoy the Freshman retreat (for those who are 9th graders)!

For fun, FYI

http://what-if.xkcd.com/11/

Pendu-problems!

Physics phriends....


Try these fun and informative problems related to all things pendulum:

1.  A simple pendulum is 1.5-m long.  How long will it take to complete one swing (a period)?

2.  A simple pendulum is 15 cm long.  How long will it take to complete one swing?  Watch units, and keep in mind that g is in m/s/s.

3.  What is the general effect of gravitation on the period of a pendulum?  If you did a pendulum experiment on the Moon, how would the results vary?  On Jupiter?  At high altitudes on Earth?

4.  You are designing a grandfather clock to swing once every 2 seconds.  How long should it be?  This will require a bit of algebra, and may be challenging at first.

5. Research what makes a simple pendulum "simple."  What assumptions are made for a "simple pendulum?"

6.  Read all about pendulums on physicsclassroom.com, if you have time.

7.  Look at these videos:

http://www.youtube.com/watch?v=vY3oiPAIS-g

http://www.youtube.com/watch?v=yVkdfJ9PkRQ&feature=youtu.be

Discuss.

Logger Pro - if you're having trouble downloading it, try to download the demo version:

http://www.vernier.com/downloads/logger-pro-demo/

HW - graphing data

Use a graphing program to plot Time (AKA Period, in seconds) versus Length.  Typically, the dependent variable is on the y-axis and the independent variable is on the x-axis.

You may use any graphing program you like.  Excel works well, though it will not graph curves.  There are online graphing programs.  My favorite is Logger Pro, which we have a site license for.  Download it here:

https://parkscience.pbworks.com/w/page/351271/LoggerPro


The password is technology


Create a graph and attempt to make some mathematical sense out of it.  Is there an equation that might be relevant to relate time/period and length?  What would it resemble?  If you come up with a tentative answer/theory, check it by looking online for an equation:  period of simple pendulum equation.

Good luck!  Bring graphs and ideas to class next day.

More pendulum business

Sorry for the delay in posting this.  No worries if you can't get to it by Tuesday.

You've had some time to "play" with the pendulum.

What is the next step?  How should you proceed?  Think about these things and write down your thoughts.

Ultimately, we are interested in some type of physical and/or mathematical relationship.  Maybe even an equation? Let's say, for example, that we want to know exactly how the length of a pendulum sets the time required for one complete swing (if indeed it does).  How can we best collect data and analyze this data?  What is "enough" data to be convinced?  What would convince you?  How and what will we graph, if anything?  What can a graph tell us here?

We'll be doing this in class on Tuesday.  Think about this problem - what is our best approach

Pendulum lab

Prepare a protocol for investigating a simple pendulum.  Think about these things:

- what variables might be important
- how would you test your ideas
- how would you record data
- how would one determine a physical/mathematical relationship