sound waves powerpoint

prerequisites for production of sound

1. a medium of transmission

2. a source of energy

3. a vibrating object that generates audible pressure

physical, psychological

sound can defined from ______ and _______ perspective

air medium

• approx. 400 billion molecules per cubic inch

• these molecules are random in motion with average speed of 1500 km per hour

• atmosphere pressure: 100,000 N/m² or 1,000,000 dynes/cm²

mass, density, elasticity

important properties of any medium

mass

amount of matter that is present

density

amount of mass unit per volume

the car example

why does smoke from planes remain but not from cars? it is because of the density of air: when there is less, it takes longer for particles to disperse smoke

elasticity

• the property of materials to return to their original shape after a force is applied

• application of force on solid, liquid, or has → distortion of either shape, volume, or both

• tendency to recover

elastic limit

limit until a medium will change form (a rubber band snapping after being pulled/stretched too far)

hooke’s law

the magnitude of restoring force of elasticity is directly proportional to the magnitude of spring displacement

Fr = -kx

Fr = restoring force of elasticity

X = magnitude of displacement of the spring

K = spring constant

stiffness

why some springs require greater force than others to be compressed or extended

more, less

stiffness less = ____ compliant

stiffness more = ____ compliant

(inverse relationship)

mass, elasticity

important properties of source of sound

newton’s 1st law

all bodies remain at rest of in a state of uniform motion unless another force acts in opposition

newton’s 3rd law

for every action, there is equal and opposite reaction

directly

amount of inertia of an object is _____ related to mass of object

length, mass, time

all other quantities can be derived from these 3 quantities

MKS system

(M = meter, K = kilogram, S = second)

cgs system

(c = centimeter, g = gram, s = second)

displacement

• change in position

• involves direction and distance

• vector quantity

vector

displacement, velocity, and force are ______ quantities

scalar

distance is a ______ quality

scalar quantities

• Mass, time, and energy are described only by reference to magnitude, they have no direction…

• any quantity that can be completely described by its magnitude only

vector quantities

a quantity that has both magnitude (size) and direction

average, instantaneous

_____ velocity refers to the total displacement of an object divided by the total time taken to travel that displacement, while _____ velocity is the velocity of an object at a specific point in time

newton’s 2nd law

the acceleration of an object is directly proportional to the net force applied to the object and inversely proportional to the mass of the object

F = ma (F = force, m = mass, a = acceleration)

trucks need more gas than cars because they are heavier

acceleration

time-rate change in velocity

delta c/time

(deltac = change in velocity)

force

• unit Newton (N)

• meaning of 1

• 1 N = 100,000 dynes

• application → distortion or change in shape acceleration

pressure

• Amount of force per unit area

• inversely related to area, directly related to force

• p=F/A [F=Force; A=Area]

• Units
  - MKS → N/m2
  - cgs → dynes/cm2

• Alternative unit is Pascal (Pa)
  - 1 Pa= 1 N/m2 = 10 dynes/cm2

momentum

mass x velocity

kinetic energy

a form of energy that results from an object in motion (types of motion = translation, rotation, vibration, etc.)

run = highest of this

potential energy

form of energy that results from object position or arrangement of parts, it is a stored energy

sit = highest of this

work

done when force succeeds in moving a body that the force acts upon, and the quantity of work is given by the product of magnitude

more of this = more displacement, more force

displacement = 0, 0 this (even with applied force)

W=Fd

work equation

MKS unit → joule
→ 1 joule= 1 N*1 M
cgs unit → erg
→ 1 erg=1 dyne*1cm

speed of sound

dependent on the characteristics of the medium

= square root of elasticity (E) / density (p)