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Lesson 02 – Forces and Structures

Read About Forces and Structures

Vocabulary

Can you find where all the definitions are in the text?

Dead loads are permanent forces acting on a structure or anything that is permanently attached to a structure, such as the weight of the roof attached to a house.

External forces are forces that act on a system from the outside.

Internal forces are forces that are created by the external forces acting on parts of a structure such as poles, roofs, or columns.

Live loads are temporary forces acting on a structure or objects that can be removed, such as the weight of books on a shelf.

Loads are forces that act on a structure, such as the weight of snow on a roof.

A structure is something that is built or constructed, such as a building.

Forces and Structures

A structure is something that holds or supports a load. For example, a garden shed has four walls that support a roof.

Structures are built for one or more purposes. A garden shed provides a place to keep garden tools dry. A locked shed will also keep the tools safe so they will not be stolen.

What Types of Forces Act on Structures?

Two types of forces act on structures—internal forces and external forces.

Internal forces are forces that are created from parts of the structure. For example, the roof of a house is heavy and pushes down on the outside walls. The roof is part of the structure of the house. If the walls are not strong enough to hold up the roof, the house will collapse. So the pushing force created by the weight of the roof is an internal force.

External forces come from things that are not part of the structure. For example, snow will push its weight down on the roof. The walls also have to be strong enough to support the weight of snow on the roof. Because the snow is not part of the structure, snow is an external force.

A roof is an example of an internal force.
Snow on a roof is an example of an external force.

Two Types of Loads

Loads are forces that act on a structure. All structures need to be strong enough to hold up under the loads placed on them. Loads are divided into two categories—dead loads and live loads.

Now Show What You Know!

Complete some questions about the reading selection by clicking “Begin Questions” below.

Read About Forces and Structures

Vocabulary

Can you find where all the definitions are in the text?

Dead loads are permanent forces acting on a structure or anything that is permanently attached to a structure, such as the weight of the roof attached to a house.

External forces are forces that act on a system from the outside.

Internal forces are forces that are created by the external forces acting on parts of a structure such as poles, roofs, or columns.

Live loads are temporary forces acting on a structure or objects that can be removed, such as the weight of books on a shelf.

Loads are forces that act on a structure, such as the weight of snow on a roof.

A structure is something that is built or constructed, such as a building.

Forces and Structures

A structure is something that holds or supports a load. For example, a garden shed has four walls that support a roof.

Structures are built for one or more purposes. A garden shed provides a place to keep garden tools dry. A locked shed will also keep the tools safe so they will not be stolen.

What Types of Forces Act on Structures?

Two types of forces act on structures—internal forces and external forces.

Internal forces are forces that are created from parts of the structure. For example, the roof of a house is heavy and pushes down on the outside walls. The roof is part of the structure of the house. If the walls are not strong enough to hold up the roof, the house will collapse. So the pushing force created by the weight of the roof is an internal force.

External forces come from things that are not part of the structure. For example, snow will push its weight down on the roof. The walls also have to be strong enough to support the weight of snow on the roof. Because the snow is not part of the structure, snow is an external force.

A roof is an example of an internal force.
Snow on a roof is an example of an external force.

Two Types of Loads

Loads are forces that act on a structure. All structures need to be strong enough to hold up under the loads placed on them. Loads are divided into two categories—dead loads and live loads.

Now Show What You Know!

Complete some questions about the reading selection by clicking “Begin Questions” below.