Sound Waves - 8/25

speed of sound and frequency are [dependent/independent]

independent. speed of sound has nothing to do with frequency

to men’s voices travel faster or slower than women’s voices?

neither. men’s and women’s voices travel at the same speed

solids are [more/less] elastic than air

more

air is [more/less] elastic than both liquids and solids

less

iron is [more/less] elastic than rubber

more

what are the 3 prerequisites for sound production?

1. a medium of transmission (air)

2. a source of energy (hand)

3. a vibrating object that generates audible pressure (table)

is a listener a prerequisite for sound?

no. just because no one is there to hear a sound does not mean it wasn’t produced

what are the 3 important properties of any medium?

mass, density, elasticity

out of air, liquids, and solids, which has the highest mass, density, and elasticity?

solids have most mass, density, and elasticity

speed of sound is determined by _____ and ____ of a medium, and therefore it _____ according to the medium

elasticity and density, changes

what is mass?

the amount of matter that is present

what is the difference between mass and weight?

weight takes gravitational force into account

if you go to the moon, will your mass change? will your weight?

mass will not change - not affected by gravity

weight will change - is affected by gravity

what is density?

amount of mass per unit volume, aka how squished together the particles are

air density [increases/decreases] as elevation increases

this explains why it is harder to breathe as you climb a mountain

decreases

what is elasticity?

the ability of a material to return to its original shape after being deformed

what is elastic limit?

the maximum extent to which a solid may be stretched without permanent alteration of size or shape - the point just before a stretched rubber band breaks

the elastic limit of air is [more/less] than liquid

less

the elastic limit of liquids is [more/less] than solids

less

quicksand has a [higher/lower] elastic limit than water

higher. it’s a solid

compare the two springs.

• the thinner spring takes [more/less] force than the thicker spring

• the thicker spring has [more/less] elasticity than the thinner spring

• a thicker rubber band is [harder/easier] to snap

less force

more elasticity

harder to snap

what is hooke’s law? give the equation and explain it

F_r = -kx, where x is magnitude of spring displacement and k is spring constant.

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

hooke’s law explains that

• if you pull a spring with more force downward, it will go back up [faster/slower]

• the more you pull a spring downwards, the more the restoring force [increases/decreases]

will go back up faster

the more the restoring force increases

what is stiffness?

how stiff a spring is = the spring constant in hooke’s law equation = k

a stiffer spring requires [more/less] force to compress

more

what is compliance?

how easily a spring can be deformed

what is the relationship between compliance and stiffness?

inverse

the thinner the spring, the more compliant

what are two important properties of the source of a sound?

mass and elasticity

what does newton’s 1st law state?

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

what does newton’s 3rd law state?

for every action, there is an equal and opposite reaction

what are the 3 basic physical properties?

length, mass, and time

name the 7 derived quantities mentioned in the lecture

displacement, speed, velocity, acceleration, force, pressure, momentum

what are scalar vs vector quantities?

scalar: has magnitude (quantity)

vector: has both magnitude and direction

what is displacement? is it scalar or vector? units?

displacement is a change in position that involves both direction and distance. vector. unit: meters in a direction

what is speed? is it scalar or vector? units?

speed measures how fast an object is moving without reference to direction, so it is scalar. unit: m/s

what is velocity? its equation? scalar or vector? units?

velocity measures how fast an object is moving with reference to its direction, so it is vector. v = d/t. unit: m/s in a direction, eg. 60 m/s to the north

what is acceleration? scalar or vector? units?

acceleration measures the rate at which an object’s velocity changes = a change in speed, direction, or both. a = v/t. vector. unit: m/s² in a direction

what is force? its equation? scalar or vector? units?

a push or pull that can change an object’s motion. F = ma. vector quantity. unit: Newton (N)

based on the equation F = ma, force is [directly/inversely] proportional to mass

directly. if it has more mass, it needs more force to move it

based on the equation F = ma, force is [directly/inversely] proportional to acceleration

directly. more force = more acceleration

based on the equation F = ma, acceleration is [directly/inversely] proportional to mass

inversely. rearrange equation so that m = F/a. an object with smaller mass will accelerate more

what is pressure? scalar or vector? its equation? unit?

pressure (p) is the amount of force per unit area. scalar. p = F/A. unit: N/m² or Pascal (Pa)

what is momentum? how to calculate it? scalar or vector? unit?

the measure of an object’s quantity of motion. momentum = mass x velocity. vector. unit: kg x m/s

what is kinetic energy? what is its equation? units?

energy that results from an object in motion. unit: Joules (J)

KE = 1/2mv²

what is potential energy? what is its equation? units?

a form of energy that results from object position or arrangement of parts. it is a stored energy. unit: Joules (J)

PE = mgh

where is potential energy highest? where is kinetic energy highest?

potential energy highest at A and C. kinetic energy highest at B (velocity is highest)

what is work? its equation? units?

work is done when a force moves an object. work = force x displacement, W = Fd. unit: Joules (J)

what is the equation for power (P)?

P = W/t = Fd/t

what is the phase difference between these two waves?

180 degrees. mirrored = 180 degree phase difference

what is the phase difference between these two waves?

90 degrees

what is the phase difference between these two waves?

270 degrees