Grade 7 Science: Forces and Structures

Define function

The purpose for why a structure is built

Define aesthetics

How a structure looks (is it pleasing to the eye) or feels, good or bad

Define structure

Any object made of parts that are arranged together to provide support

What is a solid structure?

A structure formed from a solid piece or combination of solid pieces

What is a frame structure?

A structure made up of a rigid arrangement of parts or components that are fastened together

What is a shell structure?

A structure with a strong outer surface and is hollow inside

What is a combination structure?

A structure made up of more than one structural form

Define force

A push or pull on an object

What does the effect of force depend on?

Magnitude, direction, location

What is magnitude?

The size/strength of the force

What is location?

The location of the object that the force is applied to

What is direction?

The direction you apply the force in

Define external force

A force applied to an object by another object or force

Define center of gravity

An imaginary point where gravity is equal on both sides of the structure making it balanced

Define load

The weight that a structure must be able to hold

What factors influence the structure of a house?

Climate, location, materials available, cost, aesthetically pleasing, natural forces, does it impact wildlife?

What are the types of load?

Dynamic, and static

What is a dynamic load?

A load that moves or shifts

What is a static load?

A load that is motionless (dead load)

What are the types of bridges

Beam, truss, suspension, and arch

What is a beam bridge?

A bridge that is supported by pillars at the ends which holds up the beam. It is flat and is the most common type of bridge.

What is a truss bridge?

A bridge that uses triangles (trusses) on the sides to hold up the load. It is lightweight and strong.

What is a suspension bridge?

A bridge that uses cables to enforce it. There are towers at the ends that hold it up.

What is an arch bridge?

A strong bridge that uses an arch to transfer the load to the pillars. This bridge can withstand heavy loads.

What is an internal force?

A force applied on the inside of an object or structure

What are the types of internal forces?

Torsion (when an object becomes twisted), Shear (when two materials slide past each other), Compression (the push on an object making it shorter), Tension or Stretching (the pull on an object making it longer), Bending (one side squeezes together while the other pulls apart making it curved)

What is compression?

When an object gets pushed inwards. This makes the shape of the object shorter.

What is tension (stretching)?

When an object is stretched apart. This makes the shape of the object longer.

What is shear?

When two sides of an object slide past each other in the opposite direction. The object looks tilted.

What is bending?

When an object becomes curved because of a combination of compression and tension. One side squeezes together while the other side pulls apart. This makes a curved shape in the object.

What is torsion?

When an object is twisted. When this happens, one side becomes vertical and the other is horizontal.

What is structural failure?

When a structure can no longer withstand the force that is acted on it making the structure break or fracture

What is structural fatigue?

When a structure is worn down by the force and is slowly breaking down

How can structural shapes increase the stability of a structure?

Certain structural shapes equally distribute weight among the rest of the shapes therefore making a structure stronger

What is a joint?

Something used to connect two or more objects

What is a fixed joint?

A joint that does not move and cannot bend

What is a moveable joint?

A joint that can move and is flexible

What are ways you can strengthen a structure?

Corrugation, lamination, using a truss, using a arch, using a tie, or using a strut

Define margin of safety

The limit within which the manufacturer believes the safety performance of a structure is acceptable

What is corrugation?

Waves like shapes inside two sheets

What are the factors taken into consideration when building for safety

How strong and flexible a structure is

What is lamination?

Connecting layers of materials together

What is a truss?

A framework of beams that form triangles

What is an arch?

It is a curved structure that equally distributes weight amongst the rest of the structure

What is a tie?

A beam that is used to resist tension

What is a strut?

A beam used to resist compression

Explain criteria for evaluating designs?

Cost (how much will it cost to build and operate), benefits (the benefits of building it and who will enjoy it), safety (is there a safety hazard, who or what can be affected), and impact on the environment (will and how it may impact, how to prevent harm).

What are complimentary forces

When two or more internal forces are acted upon a structure