Material Behavior (02:18)
When deciding what building material to use, one must consider how the material will behave. How it responses to different forces is important to its construction.
Forces in Action (04:25)
Force causes materials to experience compression or tension. Different forces are explained using a basketball hoop.
Translational and Rotational Forces (03:22)
When two forces act on the same point, equilibrium occurs. When force is applied at different points, it causes torque.
An expert uses a book and a box to demonstrate cantilevers. Forces cause the book to fall after a certain amount of its weight is pushed over the edge of the table.
Stable Equilibrium and Free-body Diagrams (02:20)
When an object is not moving, it is in stable equilibrium. A free-body diagram is a diagram of an object and the forces acting on it.
Materials and Their Properties (02:47)
During the building process, the weight of materials does not matter as much as the stiffness of materials. Materials with less stiffness are used if a bridge needs to sway to protect the structure. Lighter material can be made stronger by weaving carbon fibers.
Different Forms of Carbon (00:53)
Materials made of carbon are strong because of the atom structure. Some materials, such as graphite, are easily broken with a sheering force.
Measuring the Properties of Materials (02:06)
Materials can be compared on the same standards by measuring properties. Tension is tested by applying the same load to each type of material.
Stress/Strain Graphs (03:29)
Learn to calculate how a force applies stress to a material. A table can show how much strain there is under different forces.
Stress/Strain Graphs: The Plastic Region (03:02)
Hook's Law can be observed in the elastic region of a stress/strain graph. Once the force is removed, the material follows a similar path back to its starting point.
Stress/Strain Graphs: Area Under the Curve (01:01)
The area under the curve of a stress/strain graph gives information about the overall toughness of the material. The area is larger for tougher materials.
Stress/Strain Graph: Units (01:11)
The vertical axis of the graph is stress and the horizontal is strain. Learn how to label a stress/strain graph and the units that are used.
Young's Modulus (00:37)
Young's Modulus is the slope of the stress/strain curve in the elastic region. Learn how to calculate stress and strain.
Brittle vs. Ductile (02:40)
Objects that are less stiff are ductile. Stiffer objects are brittle. Learn to plot types on the stress/strain curve.
Composites: Reinforced Concrete (00:59)
Concrete is strong under compression but weak in tensile stresses. Steel beams are added to concrete to make it stronger.
Composites: Carbon Fibers (00:31)
Carbon fibers are encased in glue to make a strong, lightweight material. Combined materials are stronger than they are individually.
Worked Examples (01:01)
The strength of materials can be easily seen on a stress/strain graph. Very ductile materials can stress to more than 500% their original length.
Question 1 (00:42)
With a stress/strain graph, it can be simple to determine how a material will act under a certain amount of stress. Learn how to find the information for Styrofoam.
Question 2 (00:57)
Acrylic is a brittle material. Learn how to find the Young’s Modulus for it using a stress/strain graph.
Question 3 (01:48)
Fracture points can show when a material will break under pressure. Learn to calculate when the material will break.
Types of Bonding (Metallic, Ionic, and Covalent) (02:28)
Materials must have atoms that are strongly bonded together to be strong building materials; strength depends on bonding type.
Materials and Nanotechnology (03:16)
Using nanotechnology, scientists can manipulate single atoms. The atoms can be moved to change the structure of the material.
Credits: Materials: How They Behave Under Load (00:23)
Credits: Materials: How They Behave Under Load
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