|Name of Activity
||Bicycle Unit: Engineering the Wheel
||bikes, force, friction, rolling, ramp, travel, wheel, tire, LEGO
||4, 5, 6
||1 Hour Total
||Using bikes as an example, students will examine the force of friction. They will apply their knowledge to build an object that rolls down a ramp and travels as far as possible.
||- To experiment with wheel sizes, shapes, and materials.
- To learn about the affect of friction on bike tire design.
- To practice teamwork and competition.
||- Ramp (made of wood, cardboard, foamcore etc.) that is approximately 25 cm high at the top.
- Tape lines to mark where to start measuring distance.
- ‘Ramp Roller Challenge’ and ‘Tire Chart’ Worksheets.
- Homemade LEGO kits (consisting of different types of wheels, axles, bushings, beams, bricks and weighted bricks).
- Other materials that cars could be constructed out of:
– Wood, cardboard, straws, old containers, art supplies, blocks, etc.
|Preparation and Set Up:
||- Create kits to make cars with.
- Make a ramp that is about 25 cm high and mark starting point on ramp and start point for measuring distance at the bottom of the ramp.
- Photocopy a ‘Tire Chart’ worksheet for each student.
- Photocopy a ‘Ramp Roller Challenge’ Worksheet for each student.
- Arrange students in pairs.
- Distribute materials.
||Wheels must respond to a lot of forces. Riders weight, Bumps and dips, Weight of the frame, Wheel itself.
Friction is a force that affects the wheels of a bike because tires are the part of the bike in contact with the road. Friction is the force that appears when two things rub together (rub your hands – makes heat). The smoother two objects sliding against each other are, the less friction there is. Microscopic ridges are what interact with each other when any two objects meet. If a wheel had no friction it would not be able to move a bike; it would just spin in one place. However, too much friction causes a rolling wheel to slow down, and makes it harder to pedal.
- Show students two different bike tires; one from a mountain bike and the other from a road bike (pictures are fine, the real thing is better).
- Have each student fill out the ‘Tire Chart’ worksheet attached to this document to examine the properties of each wheel and the reason that property is there.
- E.g., MOUNTAIN BIKE WHEEL - Property: wide tires, Reason for Property: More surface area on the ground for better stability
- Discuss, as a class, the different forces on tires and the design features that account for these forces.
- Have students build an object that will travel the farthest once it rolls down a ramp.
- Remind the students that you used the word “object” because they do not have to design anything that resembles a car.
- Once students have built their original design, let the students test their design on the ramp.
- Students should record their results on the ‘Ramp Roller’ worksheet: the distance traveled from the bottom of the ramp, and the design changes that they make.
- Have students redesign or make changes to their original design and retest.
- Students get a total of three trials.
- When everyone has finished bring the class together for class discussion.
- Talk about different factors that affected the distance the cars traveled.
- Talk about how weight might have affected their cars.
- Tell students that, for some of their designs, adding weight did not help because it added friction to the place that the axle went through the beam. The more mass on the car the more friction there would be between the wheel’s axle and the hole that supported the rest of the car.
- Compare different designs.
- Which design was the best?
- How could other designs be improved?
- Review how friction affected designs, and point out all the different places that friction had an effect on a vehicles performance for each model.