7D: Structures & Forces Flashcards
The 3 main types of structures are:
Shell, Frame, and Solid.
What is a solid structure?
Formed from a solid piece or a solid combination of pieces of some strong material. A solid structure has little to no space inside of it. Solid structures are usually stronger than frame or shell structures but are often heavier and harder to move.
What are some examples of solid structures?
Rock, tree, apple, cement, gold bar, hockey puck, etc.
What is a frame structure?
Made up of rigid arrangement of parts or structural components fastened together,
The strength of a frame structure comes from the way the components are joined. They are also lighter than solid structures and can be both 2D, and 3D.
What are some examples of a frame structures?
Skeleton, snowshoes, glasses, bed frame, chair, easel, spider web, etc.
What Is a shell structure?
Has a solid outer surface, which may be rounded or flat in shape, and a hollow inner area.
Shell structures with a rounded outer surface are usually stronger than those with a flat outer surface, because the curved areas distribute the load around the whole surface.
Having a hollow interior means that shell structures are lighter than solid structures. They are also often stronger than frame structures and are therefore commonly used to provide protection.
What are some examples of shell structures?
seashell, dome, fan cover, snow globe, etc…
What is the difference between structural strength and structural stability?
Structural strength refers to a structure’s capacity to hold itself up, as well as any weight added to it.
Structural stability is a structure’s ability to maintain its position even when it is being acted on by a force.
What is the difference between a structure and a function?
A structure is the physical make up/support of an object/matter. The function is the use/purpose of those structures.
What is the function of an inukshuk (pronounced “in-OOK-
shook”) ???
This structure, found across the Canadian North, is a unique symbol of Inuit culture.
- It expresses “joy and much happiness” to anyone who encounters it.
- Many types of inukshuit also serve as signs, providing valuable information for travellers.
- Some inukshuit point in the direction where, traditionally, caribou herds have been hunted.
For this reason, they must be clearly visible, stable, and strong.
True or False? Two ways you could classify structures is into human made and naturally occuring structures.
True. In fact, many human made structures are based on naturally occuring structures. (ex: scuba diver paddles are based off of a duck’s webbed feet).
What is meant by the term aesthetics?
Aesthetics refers to the pleasing appearance or effect that an object has because of its design.
What is force?
A force is a push or pull that tends to cause an object to change its movement or shape.
The actual effect of a force on a structure depends on three things:
- the magnitude, or size, of the force
- the direction of the force
- the location where the force is applied
What is a vector? How are they related to forces?
A vector is an arrow that represents the direction, magnitude, and location at which a force is applied.
What exactly is a “Newton”???
The standard unit for measuring force is called the newton (N). One newton is the amount of force needed to hold up a mass of 100g.
What are external forces? Can you provide an example?
An external force is a force that is applied on a structure by something else.
Example: When you walk into a wind or stand in waves, the force you feel acting on your body is an external force. To remain standing, all structures on Earth must be able to resist the force of gravity pulling on them.
What is an internal force? Can you provide an example?
An internal force is a force that one part of a structure exerts on other parts of the same structure. In other words, internal forces are forces that act within a structure.
For example: elastic bands return to their original position after being stretched due to tensile strength and elasticity.
What is meant by the “centre of gravity”?
The estimated point at which gravity is acting as a downward force on a structure. Can be changed based upon the size, shape, and orientation of the structure.
The lower the centre of gravity is, the more balanced something will be. This is why wrestlers will get into a low fighting stance during competition.
What does the term base of support refer to?
The base of support is essentially how wide the bottom of an object is that it can balance on. For example a pogo stick has a very narrow base of support where as a skateboard has a much longer base of support.
The wider the base of support, the more balanced something will be.
What does the term symmetry have to do with balance?
If something has “symmetry” then it is a balanced arrangement of mass that occurs on opposite sides of a line or plane, or around a centre or axis.
For a symmetrical structure to be stable, its mass must be distributed equally around the centre of the structure’s base.
What is meant by the term load?
A load is an external force on a structure. The weight of the books in a bookcase is a load on the bookcase. The weight of the bookcase itself is also a load.
What is a beam bridge? What type of structure supports a beam bridge?
The beam bridge is the most common bridge used. A simple beam bridge is flat and is supported at its two ends by columns/piles. A longer beam bridge may be supported by additional piers (vertical supports).
What is a truss bridge? What geometrical shape is responsible for the structural strength of the bridge?
A truss bridge is a lightweight but strong bridge, made of trusses (triangle-shaped frames) along its sides. It is these triangular trusses that make the bridge durable and strong.
Describe a suspension bridge, what is the function of the cables?
A simple suspension bridge hangs between two ends (they may be trees!) that hold it up. A modern suspension bridge has tall towers on either end that support the main cables holding up the bridge. The main cables are anchored in concrete at each end of the bridge. Smaller cables, which support the roadway, are suspended from the main cables.
What is an arch bridge and how do loads/forces transfer throughout the structure?
An arch bridge is designed to withstand heavy loads. The dynamic load of people and other traffic causes each piece of wood or stone in the arch to push against the piece next to it. This push is eventually transferred to the end supports, which are embedded in the ground. The ground pushes back (resists), and this resistance is passed back through all the pieces creating the arch.
What type of force is displayed in the image shown here?
Tension, an internal force.
What type of force is displayed in the image shown here?
Shear, an internal force.
What type of force is displayed in the image shown here?
Compression, an internal force.
What are complementary forces? Can you think of an example of a complementary force?
When different kinds of internal forces act on a structure at the same time, they are called complementary forces.
Bending is an example of complementary forces at work. One side will display
What type of structural failure is shown in the image here?
Deformation
What type of structural failure is shown in the image here?
Buckling
What type of structural failure is shown in the image here?
Separation of Components
What type of structural failure is shown in the image here?
Shear
