Formal lab guidelines

FIRST - THIS IS NOT YOUR HOMEWORK FOR NEXT CLASS. A draft lab will be due in TWO classes (E) or THREE classes (C).

The homework for next class is the previous blog posting (for E), and the homework posting before that (for C).

Lab format.

Typically, each lab should have the following items:

Title
Your name
Lab partner name(s)
Date performed

Purpose of experiment - a line or two telling me the purpose of your work

Hypothesis (where desired, as it is for this wave lab) - what do you anticipate will be true?

Introductory remarks - "In this experiment, we blah blah blah...." These can be short - it's the place where you say anything special about your approach to the problem.

Data tables - don't forget units

SAMPLE calculation, including relevant formulas used

Graphs, where relevant - there may be no relevant graphs for the wave lab. That part is up to you. Don't forget the units and axis labels.

Conclusion - To me, this is the meat of the lab report. Here are questions to consider:

Discuss the extent to which your hypothesis was validated (or rejected).
Discuss sources of error - be specific. Saying "human error" is somewhat meaningless.
Give suggestions for improvement.
Tell me something you learned and/or liked about the experiment.

The conclusion may be a few paragraphs or a couple of pages (or more, if you write a lot). Be specific, write well, use good grammar and spelling, etc.

In every case, you will be encouraged (but not required) to submit a draft lab. I will get it back to you the same day (in your mailbox) with some comments. The formal lab is typically due the class after that.

Points are deducted for late labs, unless there are extenuating circumstances.

Homework for E block class (and for C block class after Sep 28)

For NEXT class (E), answer these questions and expect to turn them in. You may use your notes, but NOT any other web resources.

1. What exactly is simple about the simple pendulum? What assumptions are made?

2. What is the connection between an oscillator (such as a pendulum or mass on a spring) and a wave?

3. If you have a simple pendulum that is 3-m long, what is its period of oscillation?

4. How long must a pendulum be so that it has a 0.25-s period?

5. What is the theoretical shape of a graph of period vs. length (for a simple pendulum)?

THIS IS DUE NEXT CLASS, TO BE HANDED IN SEPTEMBER 30.

Board notes (from E block class)

Homework

E block - see yesterday's assignment

C block - see yesterday's assignment for the E block class

Thanks!

Homework

C block

Finish HW from last class - definitions, etc. If you've done that, investigate the meaning of: harmonics, as they relate to waves on a string. We will begin a formal lab on Monday.

E block

You began a lab last class. Prepare a data table for formal collection. It's should contain the following variables: string length, harmonic number, wavelength, frequency, speed.

Also - now that you know A little about the experiment, write a short hypothesis related to this question: what relationship exists between frequency, wavelength, distance, harmonic number and wave speed? If you cannot suggest a relationship for all the variables (and that's totally understandable), suggest some kind of expected result. Your formal lab will begin with that hypothesis.

Thanks!

Wave homework

Sorry for the delay in posting.

Please investigate and/or define the following wave words:

Wavelength
Period
Frequency
Amplitude
Reflection
Refraction
Interference
Superposition

The last 3 are tricky.

Thanks, and sorry for the wait.

Graphing

Hiya.

For next class, download and play around with LoggerPro:

https://parkscience.pbworks.com/w/page/351062/FrontPage

Scroll down to "Computing at Park". The password (which you may need to open the program) is: technology

Enjoy!

Also, use Physicsclassroom.com to investigate the connection between oscillations and waves.

http://www.physicsclassroom.com/Class/waves/

Lessons 0, 1, and 2 are worth exploring.

See ya soon, see ya on the Moon!

Pendulum revisited

Use the data for the pendulum period versus the length.

Plot a graph of period versus length. Remember unit and axis labeling.

Is there a mathematical relationship that you can see?
Can you predict what an equation (of period versus length) might resemble?

Look up the following:

Period of a simple pendulum.

Usually, period is represented by a T, in seconds, and length is given as L (in meters). See if you can find an equation for this relationship.

Does this equation seem correct for your graph?

In general, this is a good place to start for class research:

http://www.physicsclassroom.com/

If you use this site, start with the physics tutorial link, and look for waves - and then Vibrations (and pendulum motion).

For next class, bring in a graph and your other findings.

Good luck!

Pendulu-mania!

You've now gathered some data for your pendulum. Your homework:

Create a graph of the data - something that pictorially represents any relationship between variables (if indeed there is any). Linear? Exponential? Nothing? Discuss. If you don't have enough data to create a decent graph, discuss trends (if any) that you see.

If you see a mathematical relationship, what does it appear to be? Can you imagine an equation type that might be happening here?

Discuss - what can be concluded so far?

Resist the urge to look up answers. Base your answers on your data.

Think about these things:

How much data is enough?
What does it take to convince someone that there is a relationship present?
What is causation versus correlation?

Anything else worth reporting?

The Whirlygig!

Physics phriends!

Welcome and thanks for an exciting first day. I don't know about you, but I'm pretty stoked for a great year.

To summarize your homework:

1. Does the whirligig spin clockwise or counterclockwise?
2. Can you reverse it (and how)?
3. Think of applications; where you've seen this behavior previously.
4. Explain! (As best you can, without research.)
5. Investigate the toilets and sinks in your home (and elsewhere, if you wish). Do they drain CW or CCW?

Thanks again, and welcome to physics!

SI Units

Howdy, and welcome to Physics!

Some comments on the first class. I speak about SI units at some length. To remind you:

Mass is measured based on a kilogram (kg) standard.
Length (or displacement or position) is based on a meter (m) standard.
Time is based on a second (s) standard.

How do we get these standards?

Length - meter (m)

- originally 1 ten-millionth the distance from north pole (of Earth) to equator
- then a distance between two fine lines engraved on a platinum-iridium bar
- (1960): 1,650,763.73 wavelengths of a particular orange-red light emitted by atoms of Kr-86 in a gas discharge tube
- (1983, current standard): the length of path traveled by light during a time interval of 1/299,792,458 seconds

That is, the speed of light is 299,792,458 m/s. This is the fastest speed that exists. Why this is is quite a subtle thing. Short answer: the only things that can travel that fast aren't "things" at all, but rather massless electromagnetic radiation. Low-mass things (particles) can travel in excess of 99% the speed of light.

Long answer: See relativity.

Time - second (s)

- Originally, the time for a pendulum (1-m long) to swing from one side of path to other
- Later, a fraction of mean solar day
- (1967): the time taken by 9,192,631,770 vibrations of a specific wavelength of light emitted by a cesium-133 atom

Mass - kilogram (kg)

- originally based on the mass of a cubic decimeter of water
- standard of mass is now the platinum-iridium cylinder kept at the International Bureau of Weights and Measures near Paris
- secondary standards are based on this
- 1 u (atomic mass unit, or AMU) = 1.6605402 x 10^-27 kg
- so, the Carbon-12 atom is 12 u in mass

Volume - liter (l)

- volume occupied by a mass of 1 kg of pure water at certain conditions
- 1.000028 decimeters cubed
- ml is approximately 1 cc

Temperature - kelvin (K)

- 1/273.16 of the thermodynamic temperature of the triple point of water (1 K = 1 degree C)
- degrees C + 273.15
- 0 K = absolute zero

For further reading:

http://en.wikipedia.org/wiki/SI_units

http://en.wikipedia.org/wiki/Metric_system#History

>

In addition, we spoke about the spherocity of the Earth and how we know its size. I've written about this previously. Please see the blog entries below:

http://howdoweknowthat.blogspot.com/2009/07/how-do-we-know-that-earth-is-spherical.html

http://howdoweknowthat.blogspot.com/2009/07/so-how-big-is-earth.html


Physics - Yeah!!!