Science

Standard 10. Levels III & IV. Understands forces and motion

4. Understands effects of balanced and unbalanced forces on an object’s motion (e.g., if more than one force acts on an object along a straight line, then the forces will reinforce or cancel one another, depending on their direction and magnitude; unbalanced forces, such as friction, will cause changes in the speed or direction on an object’s motion)

5. Knows that an object that is not being subjected to a force will continue to move at a constant speed and in a straight line

Students will:

• understand the characteristics of motion and friction

(Note: Ideally, each group would have an assembled coaster car that has already been tested on a flat track and down a ramp.  To build a Coaster Car each group will need:

• one basic chassis made of a small plank of foam-core
• two axles and  made from large straws with carriage bolts running through. These are attached using masking tape to the chassis
• 6 wing nuts to hold the wheels
• 2 hex nuts to hold the wheels
• 4 wooden wheels that fit on carriage bolt {can be purchased at a hobby store})

• carpet
• corrugated cardboard
• white board surface (or other slippery, smooth surface)
• small, uniform tiles

• friction: the force that resists relative motion between two bodies in contact
• rolling friction: see above link
• speed: rate of motion

Step 1. Investigate the Opportunity: (50 minutes)

In this stage, groups of students will be introduced to the challenge. They will have an opportunity to investigate samples of several different surfaces that their coaster car will be tested on. The goal is to design a wheel for the coaster car that will improve the performance (speed) of the coaster car on the given surface by increasing/decreasing the friction.  Students will begin by investigating the performance of the standard wooden wheels on their chosen surface and getting an average speed for the standard coaster car. (Note: other standards of success may be established at this point such as smoothness of ride, how far it travels once off the ramp, etc.)

(Note: Ideally each group would have an assembled coaster car that has already been tested on a flat track and down a ramp. See materials above for what is needed to build a coaster car.)

1. Assign students into small groups of three or four.  Give them the challenge: The goal is to design a wheel for the coaster car that will improve the performance (speed) of the coaster car on the given surface by increasing/decreasing the friction.  

2. Each group should be assigned one alternate surface - carpet, corrugated cardboard, smooth surface, small uniform tiles - to investigate. They may take photos, draw sketches, and/or describe this surface by recording this in their notebooks.

3. Students should test their “normal” wooden wheel according to the standard of success you have established such as speed (see above for other ideas). Students should make careful record of the data they collect throughout this investigation. Both qualitative and quantitative observations should be made and many trials should be performed to create a dependable baseline. This should be recorded in the students’ notebooks.  All tracks are returned to the teacher. (In this version, students are given very limited access to their assigned track material until a later stage.)

Step 2. Brainstorm Ideas:  (30 minutes plus home extension time)

1. Individuals students will brainstorm how to increase (or decrease) the friction of their wheels based on their given surface.

2. They will begin by collecting materials from home to incorporate into their wheel designs.

3. Sketches should be made of each wheel design along with predictions of how each wheel design will increase/decrease the friction as well as how this might affect the performance of the coaster car on the given ramp material. (This should build on a prior lesson on rolling friction.)

Step 3. Edit + Develop Ideas: (50 minutes)

1. Students will compare sketches of their preliminary wheel designs within their group and begin creating mock-ups or models of their wheels.

Step 4. Re-frame the Problem: (50 minutes)

1. The students will now have access to small samples of the modified track surfaces. They will test their wheel designs on their assigned track material and further edit their designs preparing samples to share with another group. (Note: Students are not given enough material to create a whole track at this point. The small sample should serve to further inform their design changes.)

Step 5. Share + Evaluate your Process and Ideas: (20 minutes)

1. Student groups will share their wheel examples with another group, visually demonstrating how they predict their car will perform on the modified track. Groups will collaborate to provide suggestions on how to improve the performance of the Coaster Car with its modified wheels on the new track material.

Step 6. Finalize the Solution: (30 minutes) and Test: (50 minutes)

1. Students will finalize their modified wheels and attach these to their coaster cars. They will also create a prediction of the car’s performance with its new wheels on the new track material using the vocabulary from the previous friction lesson.

Step 7. Articulate the Solution and Process: (one to two 50 minute periods)

1. Students should now have sufficient data to create a report on the results of their design process. Each group should create a presentation board including (but not limited to):

• Starting data (wood wheels on new track)
  
• Evidence of the group’s process while designing their wheels
  
• Their coaster car with modified wheels
  
• Group’s prediction of performance with rationale
  
• Final results (modified wheels on new track)
  
• Concluding statement

This can be shared with others as a gallery walk or presentation style.