# Week 2 (Aug. 19 - 23)

**Reading:**PSE Chap 1, Physics and Measurement

**Topics:**This week, we finish our discussion length, time and other units, unit conversions, dimensional analysis. We will also focus on

*orders of magnitude*and how to

*estimate*quantities.

**Quiz**on Monday of this week!

**Week 2 HW and Pendulum lab:**

**Pendulum laboratory experiment**- Study the guidelines for how to keep a laboratory notebook.
- Suspend a pendulum bob from a thin cord. Pull it back, release it, and measure the time for one oscillation. How far did you pull it back? How long was the pendulum? What is the weight of the bob? Be sure to estimate and record the uncertainty in each of your measured quantities.
- Repeat this procedure for several different cord lengths, recording your procedure and data in your lab book notebook
- Using
*Logger Pro*, make a (beautiful) plot of the period of oscillation as a function of the pendulum length. Be sure to clearly label your axes and make your data points large and visible (but not too large). - Does your data behave as you expect, based on dimensional analysis? Fit an appropriate mathematical function to your data to see if it matches your expectations.
- Print your plot and fix it securely into your laboratory notebook. Explain what you learned from your experiment and what you would do differently if you were to do the experiment again.
- Scan and submit all of the laboratory notebook pages from our pendulum experiment this week.
**Spiders estimation:**Estimate the number of spiders inside your house. Explain your reasoning. Solution.**Ping pong balls estimation:**Estimate the number of ping pong balls can be placed (in a single layer) on the surface of Lake Michigan? Do not look anything up anywhere. What quantities do you need to estimate? What assumptions must you make? Remember, when estimating, use only one significant figure.**Answer: I'll estimate that the length is about 300 miles and the width is about 70 miles. Maybe 500 km long by 100 km wide. That's 50,000 km^2. A ping pong ball has a radius of about 2 cm. So its area is about 10 cm^2. So about 5 x 10^13 balls will fit.****Orbital speed estimation:**Estimate the speed of the earth as it orbits around the sun. Hint: the earth is bit under 100 million miles from the sun. Solution.

**Registration for College Credit:**Wisconsin Lutheran College is requiring students in this course who are interested in obtaining college credit. Please apply in the application link below for each class you are wishing to apply for college credit. This must be approved by Friday, September 27.

https://admissions.wlc.edu/register/foundations

Once students apply we will wait for Wisconsin Lutheran College to confirm eligibility and requirements for college credit and communicate out further information. Please reach out to Mr. Davis if you have any questions.

**Classroom problems:**As a reminder, these are some of the problems we worked out in class…

- Dimensional analysis: determine how the period of a pendulum depends on its length and the acceleration of gravity.