Students look at issues with using rollers: the sled gets to the bottom of the ramp, but won’t keep going. Also, the rollers separate from the sled and may keep going after sled stops. To solve these problems, students invent ways to attach things that roll to the sled – thereby inventing the wheel! A sled with wheels is a car.
- Copy worksheet for “Materials I used for my car” (Download below)
- Ramps, ramp stands, sleds and rollers from Lesson 6
- Wooden skewers, straws, and stirrers (for making axles)
- Plastic wheels, beads
- Masking tape, rubber bands, bulldog clips, clay (for keeping wheels on axles)
- Two-gallon bags for storage of students’ cars; markers for putting a name on each one
The problems with rollers:
Set up one ramp with rollers, and review what happened with them:
- What happened when we used these rollers?
- What problems do you see with using them?
- Create a class chart listing the positives (what’s good) and the negatives (what’s bad) about using the rollers. Help students notice that the rollers don’t stay with the sled and the sled stops. What are some solutions for fixing the problems?
The solutions: Have students try their solutions.
These might include attaching the rollers to the sled in some manner using masking tape, glue etc.
- How well did each solution work?
- What else could we attach to the sled that would allow it to roll?
After students have worked with the rollers, show them the plastic wheels:
- What are these for? What should we call them?
- How could you put these on the sled so it will have its own rollers, and won’t lose them at the bottom of the ramp?
If students have difficulty, call attention to their own experiences with rolling things. Students will probably come up with examples such as a shopping cart, wheel chair, wagon, rolling suitcase, tricycle, toy car, etc. Use this example in the next question:
- _What does a ___________ have that makes it easy to go up and down?_
- How could you use the same idea to make your sled go down easily, and keep going when it hits the bottom?
Provide students time to experiment with the materials. Their problem is to come up with a way of attaching two skewers or stirrers (axles) to the sled, and then adding a wheel on each side of each axle. The axles can be taped, pushed through the corrugations or held with rubber bands. The wheels can be slid on from either end. At first, the wheels will tend to fall off, but students will probably come up with the idea of adding tape, rubber bands, clay, or putty to the ends of the axles to keep the wheels on. If students get stuck, encourage them to be creative, and see what other children are doing.
While students are making cars stop periodically to give students an opportunity to share and discuss how they are making their cars.
On chart paper, make a list of each of the materials, with a sample of each one. On the worksheet, each student should draw and write the name of the car parts they used. Introduce functional names for the parts:
- You are using this stick to hold a wheel. Something that holds a wheel is called an axle.
- A piece of tape, rubber band or clay used to keep the wheel from falling off can be called a stop.
They should also record how many of each part they used.
Make sure each student’s name is written on his or her car. Provide each student with a plastic bag for storage. Collect unused materials and save them for future lessons.
- Students design and make a car that has its own wheels
- Students discover and solve design problems, such as wheels that fall off
- They identify and record the names and numbers of each part using names that describe their functions