Physical Sound - Materials

Question 0

What are the five types of bonds and their strengths?

Answer 0

Question 1

What are the forces holding all materials together called?

Answer 1

Bonds

Question 2

State Newton’s third law of motion in plain English and as a formulaic expression.

Answer 2

For every action there is an equal and opposite reaction.

Question 3

Sound moves better and faster through materials with what characteristics?

Answer 3

Materials more strongly bonded and with closer molecular masses.

Question 4

According to Newton’s third law, how does sound travel through materials?

Answer 4

By Newton’s third law, if one molecule gets too far from its neighbor it will be pulled back, and likewise it will be pushed away if two get too close. Thus sound travels through materials by causing a cascade of moving masses within this electrostatic bonding structure.

Question 5

What quality of matter, in addition to mass, allows it to store mechanical energy and makes sound vibrations possible?

Answer 5

Elasticity

Question 6

Young’s modulus is an expression of what?

Answer 6

Stress divided by strain

Question 7

If a point of material is disturbed in space, it changes its relationship to its neighbors. Increased and decreased forces of attraction and repulsion act to pull the arrangement back into what?

Answer 7

Equilibrium

Question 8

When matter that has been disturbed returns to its original configuration, with everything moving back to its rest point, all the energy held is released and the material is said to be what?

Answer 8

Restored

Question 9

What is an elastic modulus?

Answer 9

The measure of the inherent stiffness of a material as a resistance to deformation under an applied load.

Question 10

What describes tensile elasticity, or the tendency of an object to deform along an axis when opposing forces are applied along that axis?

Answer 10

Young’s modulus (E)

Question 11

What modulus extends Young’s modulus to three dimensions?

Answer 11

The bulk modulus (K)

Question 12

What is the term for how closely a material’s mass points are packed together?

Answer 12

Density

Question 13

What is the formula for finding density, given mass and volume?

Answer 13

measured in kilograms per cubic meter ( kg/m³)

Question 14

What is the difference between elasticity and plasticity?

Answer 14

When a point stores energy elastically the energy is recoverable, and it is stored in a force. Plastic materials have points that don’t return to their original positions, and after moving relative to each other they stay deformed.

Question 15

Which structure tends to give purer tones, homogenous structures, where each bit of the material is largely the same as all the other bits, or heterogeneous structures, where the material is composed of many different bits next up?

Answer 15

Homogenous structures

Question 16

Given an applied force and the strain it causes on a material, what is the stiffness of the material?

Answer 16

Stiffness (k) is the distance (strain) a rod of material will move elastically for a given force (stress).

Or

Question 17

When referring to elasticity and restoration, what is strain?

Answer 17

Strain is the distance a material will move elastically when stressed by a force.

Question 18

When referring to elasticity and restoration, what is stress?

Answer 18

Stress is a given force applied to a material, which induces strain and moves the material elastically.

Question 19

What is the formula to find the stiffness of a string or rod?

Answer 19

Where k is stiffness

• A* is the cross-sectional area
• E* is the elastic (Young’s) modulus
• l* is a total length

Question 20

The bulk modulus (K) is an expression of what?

Answer 20

How much a volume of material decreases for a certain pressure.

Question 21

What is Poisson’s ratio v?

Answer 21

The resulting ratio of the fraction (or percent) of expansion divided by the fraction (or percent) of compression.

In layman’s terms a “squash factor” where expansion or compression on an axis causes the opposite reaction on one or both of the other axes.

Stretching a rubber band expands its length, but compresses its width.

Question 22

Given the Poisson ratio v and the Young’s modulus E what is the formula to calculate bulk modulus K?

Answer 22