First, review concepts from last week: hypothesis, constant, variable
Next, introduce Galileo. The kids in this group who are also taking co-op history will be studying him later in the fall -- the co-op history class for grade 3-5 is using Story of the World 3, Early Modern Times -- mention this to the kids. Ask what the class already knows about Galileo. One boy mentions that he worked with gravity. Explain that he also worked with pendulums and telescopes. He's considered one of the father's of modern science.
For pendulums, describe how he would watch the chandeliers swinging in the chapel and wonder about the period (time to swing back and forth). Point out to the kids that Galileo didn't have a watch since they hadn't yet been invented, so he sometimes used his pulse to measure elapsed time. Draw a picture of a pendulum on the board, and ask the class what things we could vary to see if we could change the period. The kids came up with length of string, how far we pull it back, how much the bob on the end of the string weighs.
Set up pendulum on edge of table by using string, electrical tape, a paper clip, and hex nuts. Use iPad stopwatch function to time a minute's worth of swings while counting the number of periods (it's really, really hard to time a single swing with a stopwatch, so I chose to do it this way). Record results. Pull pendulum back higher, count, record (actually, I let the kids do this part); add more weight, count, record; shorten string, count, record. Discover that the length of the string is what governs the speed at which the pendulum swings. Write Galileo's mathematical equation on the board and explain it briefly to them (many blank faces while explaining pi and square roots). Mention that another way to change the period is to go to, say, Jupiter where the gravity is different ... digress into discussion of why this isn't a viable field trip option, and why H claims if we went to Jupiter we'd be "stuck". And quick mention that Jupiter is so big its gravity makes the sun wobble (bonus material!).
For gravity, discuss the question of whether heavy things fall more quickly than light things. Drop feather and hammer as example. What would happen if we ruled out air currents? Hold up ping pong ball and golf ball; drop simultaneously on the table (which is loud). Show Youtube video of hammer/feather drop on moon during Apollo 15 mission (which the high school physics class at co-op ALSO watched this week).
Discuss that Galileo didn't have slow motion cameras, etc., to use to figure this stuff out, so he did a lot with incline planes. Discuss problems of friction, and the advantages of waxing a slide on the playground. How does all of this relate to sledding in the winter? (We live in a hilly area -- the kids are pretty savvy on comparative advantages of sled-riding positions.) Segue into our engineering project of the day: Getting a ping pong ball down a zip line.
Some of the kids LOVED the engineering project. Some didn't have time to finish their designs, while some managed multiple tries. A couple didn't even try to make anything -- I need to figure out why that is, and see if it's something we can work on. For example, if it's fear of failure, the entire point of the exercise is to mess around and probably fail, and then think up new ways to work around the failure. In any case, I plan to have more engineering projects through out the year, as long as my supply of paper cups, string, and duct tape holds out.