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