Author: STOMP Time: 1 one-hour class period Description: 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. Grade Level:
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 Setup:
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.
Wheels must respond to a lot of forces.
Bumps and dips
Weight of the frame
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. Vocabulary:
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.
This activity fulfills the Massachusetts Frameworks Curriculum Standards for Technology/Engineering for grades 3-5 and 6-8:
1. Materials and Tools
Central Concept: Appropriate materials, tools, and machines extend our ability to solve problems and invent.
1.1 Identify materials used to accomplish a design task based on a specific property, e.g., strength, hardness, and flexibility.
1.3 Identify and explain the difference between simple and complex machines, e.g., hand can opener that includes multiple gears, wheel, wedge, gear, and lever.
2. Engineering Design
Central Concept: Engineering design requires creative thinking and strategies to solve practical problems generated by needs and wants.
2.2 Describe different ways in which a problem can be represented, e.g., sketches, diagrams, graphic organizers, and lists.
2.3 Identify relevant design features (e.g., size, shape, weight) for building a prototype of a solution to a given problem.
2.4 Compare natural systems with mechanical systems that are designed to serve similar purposes, e.g, a bird's wings as compared to an airplane's wings.
2. Engineering Design
Central Concept: Engineering design is an iterative process that involves modeling and optimizing to develop technological solutions to problems within given constraints.
2.1 Identify and explain the steps of the engineering design process, i.e., identify the need or problem, research the problem, develop possible solutions, select the best possible solution(s), construct a prototype, test and evaluate, communicate the solution(s), and redesign.
2.4 Identify appropriate materials, tools, and machines needed to construct a prototype of a given engineering design.
2.5 Explain how such design features as size, shape, weight, function, and cost limitations would affect the construction of a given prototype.
6. Transportation Technologies
Central Concept: Transportation technologies are systems and devices that move goods and people from one place to another across or through land, air, water, or space.
6.4 Identify and explain lift, drag, friction, thrust, and gravity in a vehicle or device, e.g., cars, boats, airplanes, rockets.