Topic: Mystery Boxes
Teacher: What observation have you made about the mystery box?
Student 1: One string pulls out further than the other.
Teacher: Anything else?
Student 2: You can only pull the string out so far. It stops.
Teacher: What do you hear or feel?
Student 2: When you pull the string you feel it catch. Sometimes it is easy to pull and other times you have to pull really hard.
Teacher: Is this box like anything you have ever seen before?
Student 1: My dad has this thing in his garage where if you pull down on one side the other side goes up?
Teacher: what does your dad use this for?
Student 1: He uses it to lift heavy things.
Teacher: Do you think the thing in your dadŐs garage is doing work?
Student 1: Yes, because it is moving something.
Teacher: Is it a machine?
Student 1: Yes
Teacher: Why do you think it is a machine?
Student 2: Because it is doing work and it is making lifting heavy stuff easier.
Teacher: Do you think that there is a machine inside the box?
Student 2: Yes, because it is moving
Teacher: But you are just pulling the string and you are doing the work, what is actually causing work to be done?
Student 1: One string is moving further than the other.
Teacher: Why do you think this is happening?
Student 2: I am not sure, but I think that there is two different pieces of string. They can be the same one because one stops and canŐt be pulled any further.
Teacher: What causes one string to come out further than the other?
Student 1: Well, just like my dadŐs thing you have to pull it over something. Like a pulley.
Teacher: What happens in a pulley?
Student one: You pull on one side and the other side goes up.
Teacher: Go get some materials and see if you can make a mystery box just like mine.
Student made a mystery box that they think is the same as the one seen in class.
Teacher: What did you make?
Student: I think I made a box that works just like yours does.
Teacher: What does your box do?
Student: When I pull on one string the other side comes in.
Teacher: How did you make it? What does the machine look like inside?
Student: I made a pulley.
Teacher: What is a pulley? How does it work?
Student: (draws a picture) If you pull on this side it will help you lift what is connected to the other side.
Teacher: Does your box do the excat same thing as my box does? Remember that my box had a ratio of the amount of string pulled out compared to the amount of string going into the box.
Student: My ratio is 20 inches out and 10 inches in or 10 inches in and 20 inches out.
Teacher: Does your machine do work?
Teacher: How do you know?
Student: It is moving something over a distance.
Teacher: What do you mean?
Student: Well, I can only pull the string 10 inches but it moves 20 inches. This means that it moved more that I pulled it.
Teacher: What would happen if you put two or more pulley into your box?
Student: It would be able to pull it further.
Teahcer: How do you know?
Student: Well, my one sring would have to be a lot longer than my other string to go around all the other pulleys.
Teacher: Is this the goal of a pulley?
Student: Well, no like to talked about in class the pulley is used to make lifting easier.
Teacher: How would this help you in really life?
Student: It would make lifting something heavey like in my dadŐs garage a lot easier.