chapter12

Question 1

How does the arrangement of atoms in a crystalline substance differ from the arrangement in a noncrystalline (amorphous) substance?

Answer 1

Atoms in crystals are in an ordered array. In amorphous materials, they are randomly distributed.

Question 2

Which of the following has the greatest density?

Answer 2

gold

Question 3

Which is denser: an object that has a density of 1000 kg/m3 or one that has a density of 1 g/cm3?

Answer 3

they’re the same density

Question 4

Iridium is not the heaviest atom found in nature. What, then, accounts for a chunk of pure iridium being the densest substance on Earth?

Answer 4

The iridium atoms are closer together in the crystalline form.

Question 5

What is the mass density of water? What is the weight density of water?

Answer 5

1000 kg/m3; 9800 N/m3

Question 6

According to Hooke’s law, if you double the force when stretching a spring, the elongation of the spring is normally __________.

Answer 6

twice as much

Question 7

Why do we say that a spring is elastic?

Answer 7

When deformed, it returns to its original shape.

Question 8

Why do we say that a blob of putty is inelastic?

Answer 8

When deformed, it does not return to its original shape.

Question 9

If a 1-kg object stretches a spring by 2 cm, then how much will the spring be stretched when it supports a 3-kg object? (Assume the spring does not reach its elastic limit.)

Answer 9

6 cm

Question 10

Distinguish between tension and compression

Answer 10

A pulled-apart object is in tension; a pushed-together one is in compression.

Question 11

Why are the cross-sections of metal beams in the shape of the letter I instead of solid rectangles?

Answer 11

To reduce the weight of the beam while preserving the resistance to bending

Question 12

Is it tension or compression that strengthens an arch that supports a load?

Answer 12

compression

Question 13

Why aren’t vertical columns needed to support the middle of domed stadiums, such as the Houston Astrodome?

Answer 13

The weight produces compression that supports the dome.

Question 14

The name given to the shape of a sagging rope supported at its ends is a __________.

Answer 14

catenary

Question 15

Which of the following is stronger per bodyweight?

Answer 15

an ant

Question 16

What does the strength of a person’s arm usually depend on?

Answer 16

cross-sectional area

Question 17

Which requires more food daily: an elephant or a mouse? Which requires more food per unit of body weight: an elephant or a mouse?

Answer 17

elephant, mouse

Question 18

Why can small creatures fall considerable distances without injury, while people need parachutes to do the same?

Answer 18

A small creature has greater surface area per unit mass, so air resistance slows it more when it falls.

Question 19

If a loaf of bread is compressed its

Answer 19

density increases

Question 20

Compared to a bar of pure gold, the density of a pure gold ring is

Answer 20

the same

Question 21

Compared to the density of a kilogram of feathers, the density of a kilogram of lead is

Answer 21

more

Question 22

If the mass of an object were doubled while its volume remained the same, its density would

Answer 22

double

Question 23

The density of a 2-cubic meter block of mass of 1000 kg is

Answer 23

500 kg/m3

Question 24

A metal block has a mass of 5 grams and a volume of 1 cubic centimeter. A piece of the same kind of metal with a volume of 2 cubic centimeters has a density of

Answer 24

5 g/cm3

Question 25

An iron block in a furnace is heated and consequently expands, which means that its density is

Answer 25

less

Question 26

A metal block has a density of 5000 kg per cubic meter and a volume of 2 cubic meters. What is the block's mass?

Answer 26

10,000 kg

Question 27

A metal block has a density of 5000 kg per cubic meter and a mass of 15,000 kg. What is its volume?

Answer 27

3 cubic meters

Question 28

A strong spring is stretched 10 cm by a suspended block. If the block's weight is doubled, the spring will stretch to

Answer 28

20 cm

Question 29

When a load is placed on the middle of a horizontal beam supported at each end, the bottom part of the beam undergoes

Answer 29

tension

Question 30

You wish to drill a hole through a horizontal I-beam supporting a bridge. To weaken the beam the least drill the hole through the

Answer 30

web

Question 31

Stone slabs are stronger under

Answer 31

compression

Question 32

The strength of a rope depends on its

Answer 32

thickness

Question 33

Doubling the thickness (diameter) of a rope will multiply its strength by

Answer 33

4

Question 34

The Gateway Arch in St. Louis, Missouri, is a

Answer 34

catenary

Question 35

The strength of a beam is most related to its

Answer 35

cross section

Question 36

A creature that is scaled up in size, keeping its proportions,

Answer 36

will be weaker relative to its greater weight

Question 37

In cold weather, your hands will be warmer if you wear

Answer 37

mittens

Question 38

If you bake cupcakes as directed for a cake, the cupcakes will be

Answer 38

over-baked

Question 39

Which has more volume, a kilogram of gold or a kilogram of aluminum?

Answer 39

aluminum

Question 40

Which has more mass, a liter of ice or a liter of water?

Answer 40

liter of water

Question 41

An elephant radiates less heat for its size than smaller animals because

Answer 41

its radiating area is small compared to its volume.

Question 42

If each dimension of a steel bridge is scaled up ten times, its strength will be multiplied by about

Answer 42

one hundred, and its weight by one thousand.

Question 43

Which geometrical shape has the least surface area for a given volume?

Answer 43

sphere

Question 44

A weightless spring is stretched 10 cm by a suspended 1-kg block. If two such springs are used to suspend the block, one spring above the other, to effectively provide one double-length spring, then the total stretch of the double-length spring will be

Answer 44

20 cm

Question 45

A spring is stretched 10 cm by a suspended 1-kg block. If two such springs side-by-side are used to suspend the 1-kg block, each spring will then stretch

Answer 45

5 cm

Question 46

An un-stretched hanging spring is 50 cm long. Suspending a 100-N block from it increases its length to 60 cm. Adding another 100-N block makes the spring's length

Answer 46

70 cm

Question 47

When a load is placed on the middle of a horizontal beam supported at each end, the top part of the beam undergoes

Answer 47

compression

Question 48

The weight of a 1-centimer cubed metal cube scaled up by a factor of 10 will be

Answer 48

a thousands times as much

Question 49

Suppose you put a chocolate layer on pieces of candy. Compared with the amount of chocolate used to cover 1 pound of large pieces, if you cover 1 pound of smaller pieces you'll use

Answer 49

more chocolate

Question 50

A 1-centimeter cubed sugar cube scaled up by a factor of 10 has a volume of

Answer 50

1000 cm3

Question 51

A 1-centimeter cubed sugar cube scaled up by a factor of 10 has a total surface area of

Answer 51

600 cm2