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Sci7- Unit 4- Topics 1-2-3
Transcript of Sci7- Unit 4- Topics 1-2-3
Forces To perform its function, every part of the structure must resist forces (stresses such as pushes or pulls) that could damage its shape or size. Structures are things that have a definite size and shape, which serve a definite purpose or function. So the Skill testing question is... How do you classify
Structures found on Earth? What is common between
these structures? What is common between
these structures? Manufactured - built by people
- many are modelled after natural structures Natural - not made by people
- occur naturally in the environment DID YOU SAY... Structures can also be classified by their Design Can you Classify these structures based on their design? what makes them unique/ different?
Don't talk about what they are made of!!! Here are the main designs! Mass Structures Can be made by, piling up or forming similar materials into a particular shape or design.
- Mountains, coral reefs are natural mass structures
- Sand castles, dams and brick walls are manufactured mass structures) Advantages: held in place by its own weight, losing small parts often has little effect on the overall strength of the structure A Layered Look... mass structures are not always solid, but are layered and have hollowed out areas for specific functions. good example is a Sandbag Wall Structure to prevent Flooding - must be heavy enough to stay in place
- must not be too heavy to compact the earth unevenly below it
- must be thick enough so it cannot be pushed out of place
- must be anchored firmly 4 Key Elements to avoid failure Frame Structures Have a skeleton of strong materials, which is then filled and covered with other materials, supporting the overall structure. Most of the inside part of the structure is empty space. - Load-Bearing Walls: these are the walls that support the load of the the building.
- Partition Walls: these are the walls that divide up the space inside the building. Speaking about houses... do you know what a "Load bearing wall" is? how about a "Partition wall"? What do you think causes "Frame Structures" to fail? Write down a list... joints, type of material, bracing, anchoring and design all must be considered in the overall structural frame construction. SHELL Structures These structures use a thin, carefully shaped, outer layer of material, to provide their strength and rigidity. The shape of a shell structure spreads forces throughout the whole structure, which means every part of the structure supports only a small part of the load, giving it its strength. Flexible structures, like parachutes, balloons and different types of clothing are a different type of shell. Shell structures have two very useful features:
- they are completely empty, so they make great containers
- their thin outside layer means they use very little material Problems in building shell structures include:
- A tiny weakness or imperfection on the covering can cause the whole structure to fail.
- Flat materials are difficult to form into the rounded shell shape. Now what about this design?
Which one is it? Mix and match Structures Some structures are combinations of different types of structures Can you make a list of 5
"Mix and Match Structures"? TOPIC 1-
Types of Structures Great! now that you are thinking about all the types of structures, what do you think the worlds TOP 5 most famous structures are? TOPIC 2-
Describing Structures And this?... What is the structure supposed to do? What was it designed for?
What is the FUNCTION? Please enter the word
into your vocabulary. Time to start listing as many Functions as you can.
Just think of a structure/object and start classifying the functions.
THERE ARE 10 MAIN FUNCTIONS Talk to those around you... · supporting (its own weight)
· containing (substances)
· holding DID YOU SAY... Please Read p.282 as a class Pretty cool that Lethbridge, Alberta held a record for longest bridge in 1909!!! Lethbridge making history Please read
silently is the study of beauty in nature.
The best designs usually 'look good' - 'aesthetically pleasing' Aesthetics Zoolander= Aesthetics Does this look good? Comment on the Aesthetics to a classmate This video shows a building bridge competition. The bridge shown here, didn't hold the most force, but received the Aesthetic Award. Look how nice and uniform the bridge is... Safety all structures are designed and built within an acceptable margin of safety Please look up Margin of Safety, add it to your notes... look in the back of your book... adding safety often means that you are adding more material... what does that mean to the overall cost? Cost adding extra strength to a structure costs money, as well as using more highly skilled workers and better materials does. Designers plan their structures to withstand conditions they hypothesize will occur.
Good design is a compromise between a reasonable margin of safety and reasonable cost. · Usually, totally unexpected events will cause even the best (well-designed) structures to fail (example: the World Trade Centre Towers). Materials the properties or characteristics of different materials must match the purpose of the structure. Reading Pages 286-287 GOLF BALL BRIDGE LAB TEAM MEMBERS: __________________________________________________________________
Question: What shapes, techniques, and designs can effectively transport
an object from one place to another?
Materials: 16 Straws
8 paper clips
50 cm of masking tape
1 golf ball
A. Bridge must span 15 cm between desks
B. Bridge cannot be attached to the desks with tape.
C. Bridge must have a track that the golf ball can roll across on.
D. One end must be higher than the other.
(golf ball must roll across on its own)
E. Only use the materials listed above.
F. Bridge must be designed in 30 minutes.
G. Minimum 3 times out of 5, it must work when tested.
H. Golf ball cannot be pushed.
I. Bridge cannot fall over during testing.
Design plans (use pencil, rulers- this is your drawing board)
Conclusion about your design (what worked best, what could be improved still): Choosing Materials When choosing materials involves weighing advantages and disadvantages of the different materials Factors to consider:
- will inexpensive material be a problem?
- is the appeal of the structure 'pleasing' over time?
3. Environmental Impact
- does the structure harm the environment?
4. Energy Efficiency
-does the structure conserve energy? Consider buying a new winter coat... what do you want from it, what things are you looking for, will you settle for anything? Read Pages 290-291-292 Write down these terms
(Define and List examples
of these terms) Mobile Joints -
Rigid Joints -
Interlocking shapes -
Thermosetting glues -
Melting- leave space to accurately define them!!! TOPIC 3-
Mass and forces Mass The mass of an object is the measure of the amount of matter in it. The mass depends on the number of particles the substance has all packed in together... Ok, so there has to be a simple way that we can compare two different masses against one another... there must be a type of measurement unit... what could it be...? primary standard of mass in Canada we use.... KILOGRAMS!
or smaller units... GRAMS! KG G how many grams are shown above? 'Kilo' means one thousand (1000) A balance is used to measure the amount of mass in a particular substance. Do you know what a triple balance beam is? Mass stays the same no matter where you are in the universe. gravity will affect the weight... Forces and Weight remember... as a small group, you have 30 seconds to define the word "Force"... GO! DID YOU SAY... Force is a push or pull on an object. The standard unit of force is called a newton (N). (1 newton of force will stretch a thin rubber band, or will be what it takes to lift up a D-cell battery) did you know... the pull of gravity - on a mass. Weight is a force and should properly be measured in newtons. (READ- Did You Know - p. 300) Sir Isaac Newton described the force that pulls objects together as the force of gravity. The gravitational forces between two objects depends on the masses of the objects and the distance between them. This gravitational force is called weight. the farther away from the earth, the less the weight. REMEMBER:
Mass is the amount of matter an object is made of.
Weight is the force with which gravity pulls on an object. Picturing Forces A force diagram is a simple picture that uses arros to show the strength and direction of one or more forces a longer arrow represents a larger force and a wider arrow represents a stronger force how would you picture the force arrows on the moving bus? give it a think... here's what I think... ok, now pick 2 (or more) of the following images to draw your own