Chapter 12: Solids Flashcards
Atoms in a solid are arranged in
A repeating or periodic array called a crystal
Metals, salts, and most minerals - the materials of Earth are
Made up of crystals
If you shine an x-ray beam on a solid and it produces an
X-ray diffraction pattern, this is evidence of the crystalline nature of the solid
X-ray wavelengths is
0.1 nm - 10 nm
Distance between atoms in a solid were
10 nm
Solids that do not have atoms arranged in a repeating or periodic array are called
Amorphous solids
Crystal structure: The following kinds of bonds can exist between atoms in a solid
1) Ionic
2) Covalent
3) Metallic
4) Van der Waals - the weakest
The properties of a solid are
Dependent upon the kind of bonds that exists between the atoms
Density
Amount of mass per unit volume
When the volume of the bread is reduced, its density
Increases
Density depends on the mass and the spacing between atoms in the material
1) Is an intrisic property of the material
2) A degree of “compactness”
3) Independent of the quantity
4) Independent of gravity
Density sometimes also expressed as
Weight density
If an object is cut in half, its density
Remains the same
Density is a ratio of mass to
Volume, and this ratio is greater for any amount of lead than for any amount of aluminum
An object subjected to external forces may undergo changes in
Shape and or/size
A body’s elasticity is
A measure of how much it changes when a deforming force is exerted on it and how well it returns to its original shape
Material that requires more force to stretch are
More elastic
Materials that do not return to their original shape are
Inelastic
The same amount of force is applied to a steel wire and a rubber wire of equal length and diameter. Which is more elastic?
Steel
When you hang a weight on a spring, the weigh applies a force to
The spring, and this stretches the spring
Hooke’s Law
The extension of a spring is directly proportional to the force applied to it
Applied force on a spring is proportional to
The displacement of the spring from its equilibrium position
Displacement can be in the form of
Extension or compression of the spring
The spring constant “k” represents the
“Stiffness” of a spring
Large k equal very stiff equals to
More force is required to stretch/compress
Small k equal less stiff equals to
Less force is required to stretch/compress
“Xo” is the spring’s unstretched position
1) “Natural length” of the spring
2) Equilibrium position
Only when displaced (stretched or compressed) from equilibrium, a force
Existed
When something is pulled on (stretched), it is in
Tension and it is causes things to get longer and thinner
Pushed in (squashed) it is in
Compression and it is causes things to get shorter and wider
Cantilever beam
A beam fixed at one end and free at the other end
Tension and Compression characteristics
1) Tension on the upper side
2) Neutral layer: no tension or compression
3) Compression on the lower side
Horizontal (simple) beam
1) Tension on the lower side
2) Compression on the upper side
Macroscopic view
It has load and compressing tension the lower layer
Microscopic view
The two arrows are corresponding and two arrows are pulled away in the ball-shaped molecules
Construction uses a steel I-beam were known as
A beam with a cross-section shaped as letter I
The shape of the I-beam maximizes strength because
The top (under compression) and bottom (under tension) have the most material
The shape of the I-beam minimizes strength because
The middle of the beam that is not under stress has the least material
A student wants to attach a swing to the branch of a tree. Three marks are made on the branch where a hole should be drilled to insert the rope. Through which mark should the hole be drilled so as not to weaken the branch?
Near the middle (B) = neutral layer
If the arch is supporting only its own weight, then the proper shape is
A catenary (Arch of St. Louis)
The catenary is also the natural shape of a chain that
Hangs between two points
An arch rotated around is
A dome (Jefferson’s monument)
Scaling is
The study of how the volume and shape (size) of any object affects the relationship of its strength, weight, and surface are
Strength is related to the area of the cross section
1) Two dimensional
2) Measured in square centimeters
Weight related to volume
1) Three dimensional
2) Measured in cubic centimeters
For increases in linear dimension, cross-sectional area and strength grow as
The square of the increase
For increases in linear dimension, volume and weight grow as
The cube of the increase
