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Science 7Unit 4: Structures and Forces

Topic 1 - 3

CH 2019

Name:_____________________

Unit 4 – Structures and Forces pg 266-349Topic 1 pg 270-281 Types of structures

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Structure: Objects that have a _____ and that has a . Function:_____________________________Forces:_________________ such as push or _________that can change the position of an object. Load: _______________________________________or supported by a structure.

Classifying StructuresThere are several different ways of classifying structures.

1. The structure’s __________2. Its ___________3. Its ___________

4. Its __________5. The _____________and parts it’s made of6. How it is______ together

A. ORIGIN 1. ______________ structures: Structure or object ______________________ have a __________________ can be made of many __________ could have simple or __________________ can serve many ____________ can be from either the__________ or _______________ part of the natural world.

Eg. both a feather and a sand dune can be considered structures.

Activity-Look at the pictures on page 270-271 and give examples of natural structures:

2. _________________________ structures: object or structure ____________________ modeled after _____________________

Activity- Look at the pictures on page 270-271 and give examples of manufactured structures :

B. FUNCTION - Ex : A bicycle, a car and a plane are all ___________________________. Same as wings, legs and paws ___________________

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C. DESIGN Design: of a structure and the _________________of which it is composed.

There are four types of designs: 1. ____________ structures -natural or manufactured structures made

with ___________________________________. Ex :

Advantage : Is held in place by its _____________

If small pieces ________________________________ it normally has ____________________________.

Disadvantages : it often has a large size and weight-it uses a lot of materials -it can__________________ the soil beneath the structurewhich can make it unstable. -the parts that hold the structure together, ex mortar, can

__________________________ which can make it unstable

? Read « Did You Know » on page 272 and answer the following questions?How many millions of cubic metres of material did it take to create the tailing ponds at the Syncrude Oil Sands project?

2. __________structures ________________________________________________ ___________________________ Ex: Advantage : easy to __________, easy to _____________o Has lots of ____________________ inside of the structure

Disadvantage : Tall structures can ___________ The different parts of the structure have to be _________________________ and assembled.

Activity – Do the activity on page 275

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3. ____________structures : a structure where a force that holds it together comes from

_____________________________ that has been carefully fastened and that needs no internal support.

Ex :

? Read « Off The Wall » on page 278 and answer the following question?What did engineers think would help improve the performance of canoes?

Advantages : completely _____________________________________ Needs very little _________________________________

Disadvantages : can have a _________________________________________ Small ___________________________________________ can ruin the

entire structure

4. Mix and Match - Many structures combine different designs Hydro-electric dams- ________structure but contains rooms inside

that are made from strong solid ___________

Airplanes- Constructed around a metal ________ but we cover the structure with ____________ that acts as a ___________

- Warehouses and other big buildings – The thick walls of concrete are _______ structures fastened to a steel _______________ structure.

- domed buildings usually use ________construction for the domes and _______ construction for the rest of the building.

Review of topic 1 page 281 #1,2Classifying Structures

Goal: Develop ways to classify natural and manufactured structures.

What to Do

Complete the table below for the structures on pages 270 and 271 of your textbook. Determine whether each structure in the left-hand column is

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natural or manufactured. In the right-hand column, identify at least one other way to classify each structure. (Hint: How have structures been described in your classes?) Be prepared to defend your choices.

Structure Natural or manufactured Can also be classified by

sand castle

igloo

planet

snowflake

brick wall

mushroom

bird’s feather

comet

sand dune

cactus

wheelchair

the Sphinx

the Eiffel Tower

clay pot

metal pipe

telephone

house/building

jigsaw puzzle

fishing net

spider’s web

parachute

umbrella

Velcro™fastener

Structures Puzzle

1. Complete each horizontal word in the puzzle, using the clues below.

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(a) The way a structure looks or the way its parts were put together

(b) Substances from which a structure is constructed

(c) The skeleton or supporting materials of one kind of structure

(d) What structures that are made or built by people or machinery are called

(e) Another word for stresses that can push, pull, bend, or twist structures

(f) The materials, dimensions, and other criteria that designers use to plan structures

(g) A word for structures that occur in the environment and are not made by people

(h) The property that describes a structure’s ability to support a load

(i) The kind of structures with a thin layer of material spread into a curving shape

(j) Shell and frame structures, sometimes with a geodesic form

2. (a) What is the vertical word in the box? (b) Define this term in your own words.

Lab: Build a golf ball bridge Page 276-277

Group members:6

1. ______________________________________________________

2. ______________________________________________________

3. ______________________________________________________

Requirements Description Successful

A The bridge must have a span of 30 cm.

BThe bridge can sit on its own, and is not fastened to anything.

C The bridge is at least 5 cm high at the starting point

D The bridge can hold a golf ball. (Without breaking)

E One end of the bridge is higher than the other

F

Only use approved materials: 20 straws, 15 paper clips, 60 cm of masking tape

G Built in 40 minutes or less

H Succeeded in 3 tries our of 5

IThe ball rolled by itself

JThe bridge did not break or bend during all the trials

Draw a possible design to suggest to your group. As you build your bridge, record changes you made to the design. Label your diagram with major features and measurements.

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Do questions 1-5, p. 277

Structures and Forces Practice Quiz Topic 1 — Types of Structures

1. All of the following structures can be classified as manufactured, EXCEPT

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A. jigsaw puzzle B. a spoon C. a feather D. a fishing net

2. A mass structure can be made by piling materials into a particular shape or design. The following are examples of natural mass structures

A. dams and mountains B. brick walls and coral reefs C. ice sculptures and sand castles D. mountains and coral reefs

3. How a structure is put together, how it is shaped and the types of materials that are used to build it are all part of the structure’s

A. design B. function C. classification D. stability

4. ‘Running bond’ is a pattern used for strength in

A. dams B. brick walls C. beaver dams D. omelets

5. Frame structures have a skeleton-like appearance and are made of very strong materials so they can support the

A. partition walls B. retaining walls C. load bearing walls D. roof and covering materials

6. Egg cartons, food cans, bottles and pipes are examples of

A. manufactured shell structures B. natural shell structures C. manufactured frame structures D. natural frame structures

Topic 2 pg 282-296 A description of structures

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1. Function : is its ________ . The functions of a structure can be .

Ex: a bridge – supports cars and people but also its own weight. Lets people cross bodies of water.

Some words that describe the common functions of structures: Contain shelter

2. Aesthetics

Secure

Communicate Brake

is the properties of an object that makes it ________ , thus its .

Three things that can have an impact on the aesthetic of a structure:

Above all engineers and architects try to keep their designs _____________________

More often than not, clean designs look __________than over-complicated busy ones.

? Read « Did You Know » on page 284 and answer the following question?Describe what is needed for a good design. Give an example of a natural structure and an artificial structure that uses this element.

3. Margin of Safety - the need for an object built or manufactured to operate as expected for a so that the ______________________

of people and health are not at risk. In a structure, a margin of safety ensures that the structure has .

ex: An example of margin of safety would be how roofs in Canada are designed to support enormous weights, so that large amounts of _______________________ ____________________.

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4. Cost - Normally, the more a structure is, the more ____________________it is to build.

According to you, why do you think this happens? A good concept is a , a balance between a and of construction.

5. Materials Developers and designers should consider the properties of the materials they choose to fulfill the . Sometimes, are used together to profit from the ______________________of these materials. Ex:

Different types of material:

1. _______________ materialsMade of _______________________________________________________ to fulfill a specific purpose Ex: ________________________________________ Ex: Plastic with nylon mesh used in garden hoses Ex: ______________________ (see figure 4.18) made of steel rods and concrete, where the steel rods support strong tension (pulling forces) and the concrete supports strong compression (pushing forces)

2. _________________material layers of _____________________________________________ together often

produce useful _____________________________ Lamination Ex: _______________________ contains a plastic film that prevents

bursting

3. Woven and knit materials _____________and adjust well to_____________________________. Ex : _________________

U.4 T.1 Lab: Tough Tissue Test p.28911

A. Problem: Which brand is strongest?

B. Hypothesis: _______ is strongest.

C. Materials: tissue A (Our Compliments)tissue B (Royale Ultra)tissue C (Scotties)beaker, weights, water

D. Data:

sample # of marbles heldABC

Wet _____

Do Analysis Questions 1-5 p. 289

Choosing Materials- Choosing one material over another means ________________________________ _________________of each possible choice.

Stronger materials are often more ____________.

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To pick the most suitable materials for a structure, architects, engineers, and designers will usually consider the following 4 factors:

1. Cost: The ____________ materials may not always be best. They can be _______________, or ______________ with They could wear out ___________or require more ________________. There are times; however, where the least expensive material could do an

______________ job.

2. Appearance: The lifespan of a structure is often considered when deciding on which

_______________ to use. Structures like bridges and buildings last a long time and so the materials they

are made from need to remain ____________ and strong over time. Structures with short lifespans, such as cardboard boxes, need not be made of

materials that ____________________.

3. Environmental Impact: Where the material comes from - is it ___________, a ___________________,

or a non-renewable resource? How it is made - does it require ___________________that is damaging to the

environment? ____________________ – does it require harmful chemicals or materials to

assemble?

4. Energy Efficiency: The cost of many structures includes more than just the __________________

_______________________. Once a structure is completed the ___________it requires to ____________ is

a function of the materials used to build it. ________________________ in homes, refrigerators, and freezers all impact

the cost of operation. The materials used in a furnace impact its ability to _____________.

6. Joints Decisions about how to fasten structures together are critical because structures are

often ______________where their parts are ___________________ There are two main types of joints:

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1. Mobile Joints: a joint that is designed to _________________; examples: _____________ and _______________. Their complicated parts are tricky to make, and they must be coated with a

_____________ so that they move _____________

2. Rigid Joints: a device designed ___________________________ a joint that allows __________________ examples a ______ and a ________

Most rigid joints fit into 5 categories:I. __________________

II. __________________III. __________________IV. __________________V. _____________ joints

1. Fasteners: Examples: __________________________________________________ A major problem with fasteners is that the _______they make _________ the

materials they fasten. Nails and staples are usually forced in the materials, which can also cause

__________________________ of the material. Bolt, screw, and dowel holes are often predrilled which doesn’t weaken the materials as

much but _______________________________

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2.Interlocking Shapes: Are carefully ______________________, in rigid and flexible materials, that can

______________________________________. Examples: ________, dovetail joints, folded seams in sheet metal, and hems in clothing.

3.Ties: ____________________________ are all examples of materials used to tie material

together. Tying material together may, simply, be done by _______or it may take special

___________ like a __________________ where the needle and bobbin thread are intertwined.

4. Adhesives: a __________________, such as glue or epoxy

cement, that is used to hold objects or materials together.

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Adhesives increase the ________ ____________and the strength of the bond by flowing into tiny rough areas on the surface of the pieces it joins.

When glue _______________ the pieces together. ______________ glues: like those found in glue guns, harden when cooled. Solvent-based glues: harden as they _____________ The strongest glues create a special kind of force between the__________

____________________________________________. Even the strongest glued joints fail under ___________________________. If the glue is stronger than the material it is bonding, _________________

_____________________________ Some adhesives can be a ____________ because the bond as soon as they

_______________. (Crazy gluing body parts together) Some adhesives can be a _____________ because of the powerful

________________________________

5. Melted joints: Pieces of ___________or ___________ can be melted together.

__________: a process in which pieces of metal or plastic are _________ together by the

______________ of heat. There are many ways to weld joints, including: ___________________

_______________________________________

__________________: a process in which a ____________________________ to a different type of material;

the melted material hardens when it cools, forming a rigid joint that hold the other material in place.

To increase the strength of the soldered joint the pieces to be joined may be ______________or ______________ together.

When soldering, the pieces must be_____________ before joining, and the melted material must be cooled slowly and carefully to avoid brittle or weak joints.

? Read « Did You Know » on page 292? What did Spencer Silver stumble across while trying to develop a glue?

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Stretch your mind see p 293:

Review of topic 2 on page 296 #2, 3, 4 Review of topics 1 & 2 on page 297 #1, 2, 3, 5, 6, 8

Quiz on topics 1 and 2 :_________________

TOPIC 2JointsREINFORCEMENT

Goal • Assess your understanding of different joints used in structures.

What to DoAnswer the following questions in the space provided.

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1. Indicate whether each joint is rigid (R) or mobile (M). (a)door hinge (b) nut and bolt holding a wheel on a car (c) ball and socket in your shoulder (d) joint where the leg of a chair is fastened to the seat (e) ball at the end of a ballpoint pen (f) joint created where the handle is fastened to a pencil sharpener (g) joint created where the handlebars of a bicycle are fastened to the frame (h) joint created where the pages are fastened in a notebook (i) joint where a computer monitor is fastened to its base

2. What might happen to a structure if the wrong kind of joint was used? Give an example.

3. Complete the table below to identify properties and uses of rigid joints. In the last column, you can describe how a joint works using words or a diagram. Give the table a title.

Title:

Rigid joint Examples Structure that uses joint How joint works

fasteners

interlocking shapes

ties

adhesives

melted joints

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Topics 1-2 Review 19

Goal Assess your understanding of terms and concepts from Topics 1 and 2.

Puzzle1. Complete the following crossword puzzle using the clues provided.

Across(c) Structures can be classified as _____ or

natural.

(f) _________ structures can support loadswithout a frame or a solid mass ofmaterial inside.

(h) The _______ on the Taj Mahal are shelland frame structures.

(j) If a dam is not heavy enough, the__________ of water may cause it to bepushed away.

(i) A structure’s purpose is called its___________.

(m) Uneven cooling can cause _________ tocrack.

Down(a) __________ is built by piling up

materials.

(b) A mass structure is held in place by its__________.

(d) __________ are structures that have a skeleton of material and empty space inside.

(e) Shell structures usually have ________walls.

(g) ________ ________ walls hold upthe roofs of frame structures.

(i) Frame structures are weakest at the__________.

(k) A turtle’s shell is a ________ structure2. (a) Identify each object as a mass (M), shell (S), or frame (F) structure.

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pop can pencil case

chair CD cassette holder

house automobile

CN Tower juice box

human body tent

igloo hydroelectric transmission tower

balloon light bulb

cardboard box car tire

Great Wall of China chocolate bar

baseball basketball

Fill in the Blanks

Complete each sentence with the correct term.

1. An important function of any structure is to support its own ____________________.

2. Most designers try to keep their designs ____________________.

3. Layers of material that are pressed or glued together are called ____________________.

4. Concrete poured around steel bars forms a ____________________ material.

5. A Tetrapak™ juice container is an example of a ____________________ material.

6. Things that are joined together by fasteners, such as nails, staples, bolts, and screws, are weakened by the ____________________ needed to make them work.

Short Answers

Answer the following questions in the space provided.

7. Why is a basketball not constructed as a mass structure?

8. Explain why cases of pop can be stacked 40 or 50 cases high without collapsing.

9. What problems would you have if your home were built as a mass structure?

10. Define criteria or specifications, and give an example.

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11. How do plywood laminations increase the strength of plywood?

12. List one place where it is essential to have

(a) a mobile joint

(b) a rigid joint

13. Name two types of adhesives.

14. How do welding, brazing, and soldering fasten materials together?

15. Give two examples of interlocking shapes.

16. Give three examples of ties used to hold materials together.

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Structures and Forces Practice Quiz Topic 2 — Describing Forces

1. Containing, sheltering, transporting, lifting ... are all words to describe a structure’s A. design B. stability C. function D. aesthetics

2. When a structure is built to withstand loads - more than it normally would carry - the structure is built with a larger A. foundation B. symmetrical base C. set of pilings D. margin of safety

3. One important criteria of good design - that is usually not written down in the specifications - is that the structure A. has a margin of safety B. is esthetically pleasing C. is cost effective D. has a solid foundation

4. The following is an example of a composite material A. a cardboard box B. tent C. drywall D. reinforced concrete

5. When choosing the most suitable materials to build a structure, architects, engineers and designers should consider all of the following before making their final choice A. cost, appearance, environmental impact, energy efficiency B. cost, color, life expectancy, impact strength C. environmental appearance, type of symmetry, type of joints needed, cost effectiveness D. flexibility, impact strength, energy efficiency, color

6. Mobile joints are used to secure materials together in a structure. All of the following joints are examples of mobile joints (allowing movement in a structure) EXCEPT A. a trailer hitch B. photocopier lid C. ball and socket joint (shoulder) D. Lego

7. Adhesives are used to bind materials together. A type of adhesive that hardens when it cools is A. thermosetting glue B. therapeutic glue C. solvent-based glue D. solvent-enriched glue

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Topic 3 pg 298-304 Mass and ForcesMass and ForcesThe metric system of measurement was created in _____________. It replaced many traditional systems with just a ___________ system. Standard SI units were set up in _________.

Look at the chart below and fill in the blanks. Check page 452 of your textbook.Units of metric system are:

Quantity Unit Symbol

lengthNanometre 1000 000 000Millimetre 1000 mmCentimetre 100cm in 1mMetre 1Kilometre 1000 m in 1km

______________________________

massGram 1000g in 1kmKilogram 1Tonne 1000kg in 1 tonne

__________________

areaSquare centimetreSquare metre

____________

force newton ______

energy Joule ______

temperature Degree Celsius ______

volume millilitre ______

Mass : Mass is the measure of the .

___________________. It ________ as long as the

amount of particles in the substance stays the same.

Your mass on Earth, the moon and in space is !

Mass is measured in which is . (Note: we normally express the smallest masses in grams (g). ) The ___________system measures mass by comparing objects to a standard mass.

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______ : a small metal cylinder has a mass of _________ and is used as a reference to measure everything else.

“Kilo” means ; therefore 1 kilogram is a . “Mili” means one ; therefore 1 milligram (mg) is a thousandth of a

gram (___________) It would take _________ mg to make one gram. Balance: a device to measure mass; many balances work by using the force of ___________.

Forces and weight – while mass stays constant, weight will ____________ if an object moves from the Earth to the moon.

Force: is a ____ that makes an object , slow down or change directions. Force is normally measured with a , also called a . is the standard unit of force in the International System of Units (SI) Very large forces, or difficult to measure forces, are often calculated by

. To completely describe a force, you need to determine both its ___ and its ____________. Isaac Newton, 1642-1727, theorized that there is a ___________ between any two objects,

anywhere in the Universe, that tries to _________ them together. Newton mathematically examined the size of this force, which he called ___________.

Gravitational Force: The force exerted by gravity on an object; measured in newtons (N); the preferred scientific term for the everyday term “weight”.

Weight is a , therefore is measured in . Gravity is a . Weight is the . Every object that has a produces a gravitational force and gravity will act on

any object that has a mass.

Gravitational force between two objects varies depending on ________________________ .

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On Earth, the object that is the closest and has the biggest is the _________________________________ . This means that all object that have a ____________________________than the earth are attracted to it or pulled towards it.

The farther away we are from the surface of the earth; the force of gravity ________________________ .

The bigger the mass of an object, the gravitational . The closer two objects are, the .

Your weight on the Earth, the moon and in space !

Ex: on the moon your weight will be 1/6 of your weight on earth. Why?

What would be your mass?

Weight can be stated as “A _____ mass has a weight of ____ on Earth”

(It’s actually ______, but 10 is close enough for most purposes)

Balance: Force Meter (spring scale):

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Weight and Mass on Four Planets

PLANET

WEIGHT (FORCE OF GRAVITY) OF THE SILVER BLOCK IN

NEWTONS(N)

MASS OF SILVER BLOCK IN KILOGRAMS

(kg)

Mercury 240 68Venus 572 68Earth 680 68Mars 266 68

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Scientific Investigation, pg. 302: CRUSH IT! How strong it is?

Question: ____________________________________________________________________

Hypothesis:___________________________________________________________________

Materials: ____________________________________________________________________

Procedure and Observations:

Shell structure Manufactured/Natural Force needed to break the structure (N)

Analysis:

1. What was a manipulated variable? ________________________________

2. What was a responding variable? ________________________________

3. What was a controlled variable? _________________________________

4. Rank the objects from strongest to the weakest.

______________________________________________________________________________

______________________________________________________________________________

5. Which shape seemed to be stronger than the others?_______________

6. What materials seemed to be stronger than the others?

a)___________________________

b)___________________________

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For ce - Sir Isaac Newton stated his " " in 1687. According to this law, “ _____________________________________ . " The intensity of the force of gravity is influenced by both the ____ of the objects and the that separates them. This simple act was one of the first major unification of physics, because it explains so much about . __________________________and the force that holds the .Note: Forces are .

We recognize them based on their . We can them Units - The units for force are . The symbol is the letter « ». Ex:

Picturing forces -A force diagram is a simple drawing that uses

___________ to indicate the intensity of one or more ___________.

Balanced and Unbalanced Forces

The direction of the arrow indicates the ______________ of the force.

The length of the arrow shows the size of the _________ Each force is shown

with an ___________The circle stands for the __________

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Balanced Force Unbalanced forceDescriptio

n

Example

What happens

Topic 3 Mass Mania

GOAL: Practice weighing objects and calculating the difference between weight and mass.

IntroductionAlthough we often talk as if mass and weight are the same, they are not. In science, mass measures the amount of matter in an object. An object’s weight involves both its mass and the strength of the surrounding gravitational pull. Mass is measured with a balance and is expressed in kilograms or grams. Weight is measured with a force meter or spring scale and is expressed in newtons. About 10 N of gravitational force pulls an object with a mass of 1kg. (To be more precise, use 98.1 N of gravitational force/kg instead of 10 N.) Therefore an object that has a mass of 50 kg has a weight of about 500 N (or, more precisely, 491 N).

What You Need- 10 objects of your choice - spring scale (optional)- balance - calculator

What to Do

Use a balance to determine the mass of ten objects. Record each mass in the table below. Then calculate the approximate weight (use 10 N) and precise weight (use 9.81 N) of each object. If possible, measure the weight with a separate scale, as well, and compare the measured and calculated weights.

ObjectEstimated

Mass (g)

Measured mass Measured weight In (N)In (g) In (kg)

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Explain why a balance is a good way to measure mass.

________________________________________________________________________

Topic 3 Extraterrestrial Mass MathGoal •Calculate the mass and weight of objects in space.Recall that weight depends on the mass of an object and the strength of the surrounding gravitational pull. On the Moon, for example, there is less gravitational pull than on Earth. Therefore, your weight on the Moon would by about one sixth on what it is on Earth.

Earth weight _________ = moon weightMoon weight _________= earth weightEarth weight _________= Mars weight

What to Do: Answer the following questions in the space provided. Show all calculations.1. The mass of a small dog, called Fido, is 20 kg on Earth. What is Fido’s mass on

the Moon?

2. Does Fido’s mass change after he eats two cans of dog food? Explain your answer.

3. Does Fido’s mass change after he chases a car for 5 km? Explain your answer.

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4. Calculate Fido’s weight on Earth.

5. Name three ways that Fido’s weight could change.

6. What is Fido’s weight on Mars, where the gravity is about one third of Earth’s gravity?

7. If Fido’s friend, Fifi, weights 24 N on the Moon, how much does she weigh on Earth? Explain your answer.

Structures and Forces Practice Topic 3 – The Mass and Forces

1. The mass of an egg-sized lump of lead and the mass of an elephant.

A. are very different B. are about the same C. are measured in Newtons D. would change if they were measured in different places

2. Weight is a force that is measured by the gravitational pull on the object. It is usually measured in

A. Newtons B. kilograms C. grams D. pounds

3. A student compared his mass and weight in two different places (Vancouver and Banff). Which statement is correct?

A. His mass and weight were unchanged. B. His mass and weight were both the same. C. His mass was the same, but his weight was different D. His mass was different, but his weight was the same.

4. “Crush It” was an investigation activity that tested the strength of a shell structure. The

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responding variable in this activity was

A. How much weight the shell could hold before it failed. B. How much mass the shell could hold before it failed. C. How long the shell performed its function. D. How many different textbooks were used as weights.

Review of topic 3 on page 304 #1, 2, 3, 4

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