Fall 2009 Day 15

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Day 15 Topics

Ball and String Demonstration
Newton's Laws
Ning Websites

Peer Instructor Reflection

Fall 2009: Day 15
Written by: Katie Kizer

Today's class was a little bit different than most. Most days the students get to explore new ideas through hands on activities while discussing and writing down powerful ideas; however, today, Emily gave more of a lectured approach. Emily stood and talked with the students about the moon first. She explained how to draw the lit portion of the moon to the students because some of them were confused. When they were attempting to draw the lit portion of the moon for their moon papers, some of them noticed a difference in what their observations were and what the picture looked like. Emily further explained that this was just because of our perspective and where we are looking at the moon from, a 2D image, or a 3D image. Emily retouched on the idea that the side of the moon that is lit is always on the side of the sun. The reason it looks different depends on where the moon is in relation to the earth at any given time. She also discussed the different kind of language that could be used in the moon papers. Some students might prefer to talk about the changing angles from 0-180 degrees, whereas other students might prefer to demonstrate the 0-360 degrees model. In either case, the lit portion of the moon gets larger as the angle between the sun and the moon grows from a new moon to a full moon; the angle between the sun and the moon gets smaller as the lit-portion of the moon becomes smaller between a full moon and a new moon.

The next topic that Emily talked with the students about was force and motion. She started off by swinging a ball attached to a string around her head. She engaged the students by demonstrating what she was talking about, and asked them what was keeping the ball attached. The students replied, the string. She explained that the ball attached to the string is always going to stay attached and go around her head. This is similar to the idea that the moon is somehow attached (by gravity) to the earth and it continues to go around the earth. This gave the students a concrete example to think about. One fascinating idea that Emily brought up today was the idea that the moon is always falling toward the earth, but since the earth is rotating and revolving, the moon will never reach the earth. This was put into simpler terms by talking about what happens if you throw a tennis ball. The ball will eventually start to fall towards the ground (because of gravity). But what if you threw the ball so hard that as it was falling toward the ground, the earth was spinning, and it never reached the ground. This is the same phenomena we see with the moon.

Emily had each student come to a table and try to push forward three different objects of the same size. One object was easy to push, the other was harder, and the third hardly budged. Although the objects had the same shape (volume), they had different weights (masses). Emily gave the students a term instead of having them try to figure it out on their own. Inertia basically involves how easy or hard it is to move something and get it in motion. She also explained that the bigger the force exerted on an object is, the bigger the acceleration will be. Also, if an object has a bigger mass, it has a slower acceleration, for the same force. To put this in to a formula, we can use Newton's 2nd Law: force=mass x acceleration. If there is no acceleration, then there must be no force; therefore, an object with no acceleration either stays at rest or keeps moving with the same speed: Newton's 1st Law. Newton's 3rd Law: for every action there is an equal and opposite reaction. We demonstrated this in class by using the two scales and pulling in opposite directions when they were attached. The same amount of Newton's (force) showed up on both of the scales.

At the end of class, each pair of students went to the computer lab to work on their ning websites. They wrote down everything they knew about thermal phenomena, the learning processes they used, their powerful ideas, pictures, and descriptions. Once again, I think this is an excellent learning tool. I like the idea of having everything displayed in one place in an organized manner.

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