HRACE Scripts


Katie Grundahl

Topic: Mystery Boxes


Seeing the Mystery Box for the first time.


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?

Student: Yes!

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.