|Name of Activity||Bicycle Unit: Materials Testing|
|Keywords||material choices, strengths, weaknesses, materials, static load, dynamic load, friction, physical properties, chemical properties, mechanical properties, elasticity, yield strength, ultimate strength|
|Grade Level||K, 1, 2, 3, 4, 5, 6|
|Time||1 Hour Total|
|Brief Description||Students will learn about different materials that bikes are made out of. Students will learn about different factors, material strength, flexibility, cost, weight etc. that affect an engineers decision when choosing a material to use in constructing a prototype/real thing.
To apply this information, students will test and rate the strength of different types of materials. They will record the strengths on a chart and compare the different materials. Students will discuss the factors that affect an engineer’s choice of materials.
|Lesson Objectives:||- To explore the factors that affect material choices for a design.
– To compare strengths and weaknesses of different materials.
|Materials Needed:||- Hot glue sticks.
– Popsicle sticks.
– Plastic spoons.
– Metal Rods (e.g. thin nail).
– Activity Worksheet.
|Preparation and Set Up:||- Print out enough worksheets for the class (either one per group or per student)
– Optional: Set up large version of real bike materials sheet.pdf or make copies for each group to look at.
– Arrange students into groups.
– Distribute materials and worksheets.
|Necessary Background||Engineers need to keep a lot of things in mind when choosing what material they will use in their designs.
A bike will have two types of loads. The Static Load – the bike frame must support itself – and the Dynamic Load – the bike frame must support changing forces of a cyclist’s weight, forces of pedaling and breaking, road’s surface (bumps, holes)
Friction – or the resistance of the road’s surface. This factor affects the engineers decision on what a tire should be made out of and how it should be designed. Road bikes want to reduce friction for faster movement v. mountain bikes, which want wide tires for increase friction to reduce falls.
Materials that engineers choose for their designs must withstand all of these forces. There are three categories of material properities that enable bikes to function to suit different purposes
Physical: Density, color, electrical conductivity
Chemical: Reactivity, rust resistance, solubility, reaction to heat.
Mechanical: hardness, stiffness, expansion, toughness
Different tests of mechanical strength are:
Elasticity: When a material can be bent and come back to its original shape.
|Extensions or Modifications:||- Give students limitation, such as cost or weight, and have them choose the best material.
– Talk about what material would be best for a different item (cars, computers, kitchen appliances, etc.).
– Add different material to the list to test.