chapter12 Flashcards
How does the arrangement of atoms in a crystalline substance differ from the arrangement in a noncrystalline (amorphous) substance?
Atoms in crystals are in an ordered array. In amorphous materials, they are randomly distributed.
Which of the following has the greatest density?
gold
Which is denser: an object that has a density of 1000 kg/m3 or one that has a density of 1 g/cm3?
they’re the same density
Iridium is not the heaviest atom found in nature. What, then, accounts for a chunk of pure iridium being the densest substance on Earth?
The iridium atoms are closer together in the crystalline form.
What is the mass density of water? What is the weight density of water?
1000 kg/m3; 9800 N/m3
According to Hooke’s law, if you double the force when stretching a spring, the elongation of the spring is normally __________.
twice as much
Why do we say that a spring is elastic?
When deformed, it returns to its original shape.
Why do we say that a blob of putty is inelastic?
When deformed, it does not return to its original shape.
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.)
6 cm
Distinguish between tension and compression
A pulled-apart object is in tension; a pushed-together one is in compression.
Why are the cross-sections of metal beams in the shape of the letter I instead of solid rectangles?
To reduce the weight of the beam while preserving the resistance to bending
Is it tension or compression that strengthens an arch that supports a load?
compression
Why aren’t vertical columns needed to support the middle of domed stadiums, such as the Houston Astrodome?
The weight produces compression that supports the dome.
The name given to the shape of a sagging rope supported at its ends is a __________.
catenary
Which of the following is stronger per bodyweight?
an ant
What does the strength of a person’s arm usually depend on?
cross-sectional area
Which requires more food daily: an elephant or a mouse? Which requires more food per unit of body weight: an elephant or a mouse?
elephant, mouse
Why can small creatures fall considerable distances without injury, while people need parachutes to do the same?
A small creature has greater surface area per unit mass, so air resistance slows it more when it falls.
If a loaf of bread is compressed its
density increases
Compared to a bar of pure gold, the density of a pure gold ring is
the same
Compared to the density of a kilogram of feathers, the density of a kilogram of lead is
more
If the mass of an object were doubled while its volume remained the same, its density would
double
The density of a 2-cubic meter block of mass of 1000 kg is
500 kg/m3
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
5 g/cm3
An iron block in a furnace is heated and consequently expands, which means that its density is
less
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?
10,000 kg
A metal block has a density of 5000 kg per cubic meter and a mass of 15,000 kg. What is its volume?
3 cubic meters
A strong spring is stretched 10 cm by a suspended block. If the block’s weight is doubled, the spring will stretch to
20 cm
When a load is placed on the middle of a horizontal beam supported at each end, the bottom part of the beam undergoes
tension
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
web
Stone slabs are stronger under
compression
The strength of a rope depends on its
thickness
Doubling the thickness (diameter) of a rope will multiply its strength by
4
The Gateway Arch in St. Louis, Missouri, is a
catenary
The strength of a beam is most related to its
cross section
A creature that is scaled up in size, keeping its proportions,
will be weaker relative to its greater weight
In cold weather, your hands will be warmer if you wear
mittens
If you bake cupcakes as directed for a cake, the cupcakes will be
over-baked
Which has more volume, a kilogram of gold or a kilogram of aluminum?
aluminum
Which has more mass, a liter of ice or a liter of water?
liter of water
An elephant radiates less heat for its size than smaller animals because
its radiating area is small compared to its volume.
If each dimension of a steel bridge is scaled up ten times, its strength will be multiplied by about
one hundred, and its weight by one thousand.
Which geometrical shape has the least surface area for a given volume?
sphere
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
20 cm
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
5 cm
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
70 cm
When a load is placed on the middle of a horizontal beam supported at each end, the top part of the beam undergoes
compression
The weight of a 1-centimer cubed metal cube scaled up by a factor of 10 will be
a thousands times as much
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
more chocolate
A 1-centimeter cubed sugar cube scaled up by a factor of 10 has a volume of
1000 cm3
A 1-centimeter cubed sugar cube scaled up by a factor of 10 has a total surface area of
600 cm2
