Students revisit the sled that won’t go down the ramp, and invent a new way to “help” it move by modifying the sled.
Copy the worksheet: "How did I get it to slide?" (Download below)
Demonstration ramp with felt surface
Ramps, stands and sleds, one per pair of students
Felt or sandpaper sheets, and bulldog clips to attach them to ramps
Card stock, weights, paper plates, spoons, washers, lids, aluminum foil, wax paper, paper fasteners, masking tape, paper clips.[Note:do not provide materials that can roll.]
Reclosable storage bags for keeping students’ work
1.Review of the sled problem: Set up a ramp per pair of students. Attach felt or sandpaper to increase the friction.Set the ramp height so the sled cannot initially slide.
What is happening here? Use the word “friction" to describe what is holding the sled back.
Why doesn’t the sled go down?
2.A new way to get it to move. Provide card stock, weights, paper plates, spoons, washers, lids, aluminum foil, wax paper, paper fasteners, tape, paper clips.Ask:
How could you use these to help the sled move down the ramp?
Provide time for students to experiment with the materials. Some students will probably come up with the idea of attaching materials to the sled. If not, help by asking:
Which of these would work to help the sled go down?
3.Class meeting: Lead a discussion of the methods students used, and which ones worked. Introduce the words design, re-design and troubleshooting.
4.Further experimenting and recording results: If students haven’t tried a variety of ideas, provide time for them to test their ideas, as well as others that students have come up with. Then ask students to record their findings on the worksheet.
5.Class chart: Make a class chart to describe what happened as a group.
6.Storage: Provide two-gallon plastic bags for storing students’ sleds. Make sure each child’s name is written on his or her bag or sled.
Students explore how re-design of the sleds can reduce friction and allow an object to move down a ramp.