Science Grade 7 - Unit 4: Structures and Forces
it can be made by piling up or forming similar materials into a particular shape or design
mass structure
structures that have a skeleton of very strong materials, which supports the weight of the roof and covering materials
frame structure
walls that support the load of the building
load-bearing walls
reasons why frame structures are the most common structure choice
they are:
•easy to design
•easy to build
•inexpensive to manufacture
walls that divide up the space in a building
partition walls
objects that use a thin, carefully shaped outer layer of material to provide their strength and rigidity
shell structure
the four functions that structures are designed for
to support, contain, protect and span
made from more than one material
complex materials
layers of different materials pressed or glued together
layered materials
what engineers must consider when choosing what materials to use when building structures (list 4 things)
•cost of material
•appearance/aesthetic
•environmental impact
•energy efficiency
where a structure's parts are joined together
joints
allowing movement while still holding parts together
mobile joints
attach parts of a structure without allowing movement
rigid joints
fasteners, interlocking shapes, ties, adhesives, thermosetting glues, solvent based glues, welding, and soldering are all forms of _____ ______
rigid joints
what instrument is used to measure force (two terms)
force meter or spring scale
two things that you need to determine to completely describe a force
Direction and its size (a.k.a. magnitude)
A simple picture that uses arrows to show the strength and direction of one or more forces
force diagram
which length of an arrow represents a larger force in a force diagram
the longer arrow
which length of an arrow represents a smaller force in a force diagram
a shorter arrow
1kg = (how many Newtons)
100g = (how many Newtons)
= 10N
= 1N
what instrument is used to measure mass
a balance
what instrument is used to measure weight (force)
spring scale or force meter
a PERMANENT load (weight) acting on a structure
dead load (aka static)
a changing or non-permanent force acting on a structure
live load (aka dynamic)
stretching a material by pulling its ends apart
tension
bend or tear the material by pressing different parts in opposite directions at the same time
shear
A force that crushes a material by squeezing it together
compression
twisting the material by turning the ends in opposite directions
torsion
A combination of tension and compression forces
bending
for example, when cars absorb the energy of a collision in order to protect the people inside of the vehicle
buckle
for example, spinning cotton or wool fibers very tightly together to make very strong fabric
twist
this is when metal weekends due to stress. This process often results in the metal cracking and breaking
metal fatigue
arches, braces, cantilevers, large columns, flying buttresses, triangular corrugations
structural components that can be used to help support heavy loads
The point in an object where the mass is evenly divided in all directions
centre of gravity (C.O.G.)
an imaginary line from a structure's center of gravity to the ground
thrust line
A rectangular or other shape is carved into the ground and concrete is poured into the gap. When the concrete hardens, the structure can be built over it
footings
cylindrical columns are sunk deep into the ground, usually until they hit bedrock under the soil. Then the structure is built on them
pilings
the principle with which the gyroscope works
spin stabilization