Dragging shoes

Discovery question

How do shoes help you walk?

Cannot resolve external resource into attachment.

Explore the friction values of the bottoms of shoes.

Engage

Cannot resolve external resource into attachment. Maria and Eduardo wondered how they could show their friends what it was like in Sticky World, where every surface is very sticky, and Slippery World, where every surface has very little friction. (Read more about these worlds in the Frictional Adventures story. "If we had sticky shoes and slippery shoes, they could wear the shoes and then they would know what it feels like!" Maria proposed. "That's a great idea," said Eduardo, "but which shoes should we pick?"

Linker Coach (engage & motivate) Why? Affective It would be fun to wear special shoes to feel like there was no friction, and another pair to feel lots of friction!

Think of several kinds of shoes. Are some of them slippery and some of them sticky, or are they all the same?

L5 currently blank L4 Think how the bottoms of shoes look different from one another. L3 Are the bottoms of all shoes made out of the same material? L2 Are some shoes designed to be more sticky than others? L1 Sneakers and other athletic shoes are designed to have a lot of friction. Are all shoes designed that way?

List your examples and how much friction you think they have.

  Materials

• Force sensor
• Shoes of different types
• Several 500 ml (16 oz) soda bottles that fits into a shoe
• Water
• Waxed paper
• Sandpaper (8"x10" sheet) - optional

Explore

1) Collect different types of shoes from students in the class. Be sure you keep track who they belong to! Make a list describing them. What are they especially good for? What is the bottom of the shoe made of?

Student name [column header with four separate text boxes below]
Type of shoe [column header with four separate text boxes below]
What's it for [column header with four separate text boxes below]
What the sole is made of [column header with four separate text boxes below]

2) Put a plastic bottle into each shoe. Add water so that all of the shoes weigh the same. You can weigh the shoes using the force sensor.

Cannot resolve external resource into attachment.

3) Use the force sensor to drag each shoe across the floor. Pull it horizontally at a slow constant speed. Record the force when the speed is constant - NOT right at the beginning when you are getting the shoe moving. Record your value for the force required to drag each shoe. This dragging force is called the force of friction.

Cannot resolve external resource into attachment.

Lab Director Coach (Planning & performing tasks) How? Strategic Remember that we're trying to determine the friction values of different shoes.

Lab Tech Coach (Gathering facts& interpreting) What? Recognition  [Note: Cynthia and Ed discussing this recognition pattern coach as a possible technical hint.  Should the coach be metacognition.] 4) Watch the graph.  Notice when it shows a steady force. Notice when you're pulling at a constant speed. 5) Notice if the graph will be steady when you're moving at a steady speed.

 
6) Record your data in the table below
Student name [column header with four separate text boxes below]
Type of shoe [column header with four separate text boxes below]
Dragging force [column header with four separate text boxes below]
 

Explain

1) Which kind of shoe bottom is most sticky (has the most friction)? [text box]

L5 currently blank L4 Look back at your data table. What do you notice? L3 Look back at your data table. Do all shoes need the same amount of force to move? L2 Can you sort the shoes by the amount of force needed to move them? L1 Which shoe needed the most force to move?

2) Which kind of shoe bottom is most slippery (has the least friction)? [text box]

L5 currently blank L4 Look back at your data table. What do you notice? L3 Look back at your data table. Do all shoes need the same amount of force to move? L2 Can you sort the shoes by the amount of force needed to move them? L1 Which shoe needed the least force to move?

Lab Tech Coach (Gathering facts& interpreting) What? Recognition Scientists use tables to record data.  Keeping your data organized is very helpful when you try to make sense of it.

Elaborate

1) Pick one shoe and set it on a piece of waxed paper. Try dragging it in the same way as before. Record the force of friction.

Cannot resolve external resource into attachment.

Friction force = [box]

2) Pick one shoe and try dragging it across a very rough surface, such as a piece of sandpaper. What surface can you find that has the greatest force of friction? Record the force of friction. [text box]

Evaluate

Maria wanted to find a game where a shoe with almost no friction would be a big advantage. It would be like her experience in Slippery World. What game would you suggest? [text box]

Eduardo wanted to find a game where a shoe with a lot of friction would be a big advantage. It would be like his experience in Sticky World. What game would you suggest? [text box]