All matter is made of _______________ Particles are constantly ______________ As temperature...

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Transcript of All matter is made of _______________ Particles are constantly ______________ As temperature...

Page 1: All matter is made of _______________ Particles are constantly ______________ As temperature increases, particles move __________ As temperature increases,
Page 2: All matter is made of _______________ Particles are constantly ______________ As temperature increases, particles move __________ As temperature increases,

All matter is made of _______________Particles are constantly ______________As temperature increases, particles move

__________As temperature increases, distance between

particles _______________What state of matter does each of these images

represent?

Recall: The Particle Theory of Matter

Page 3: All matter is made of _______________ Particles are constantly ______________ As temperature increases, particles move __________ As temperature increases,

VibrationImagine a pendulum:

Point #2 represents the equilibrium position.

Points #1 and #3 are equal distancesaway from equilibrium.

vibration: the cyclical motion of an object about an equilibrium point (one back and forth motion of the pendulum)

Page 4: All matter is made of _______________ Particles are constantly ______________ As temperature increases, particles move __________ As temperature increases,

What’s happening to the energy of the bob as it goes through each vibration(i.e. goes through a cycle)?

What if you were looking at the motion of particles instead?

Page 5: All matter is made of _______________ Particles are constantly ______________ As temperature increases, particles move __________ As temperature increases,

Mechanical WaveTransfer of energy through a material due

to vibrationThe material is called a medium

Can be solid, liquid, or gas

How long a vibration can continue in a medium depends on how much energy is gained/lost by the medium in the vibration. (usually very little)

Page 6: All matter is made of _______________ Particles are constantly ______________ As temperature increases, particles move __________ As temperature increases,

Net MotionThe displacement of a particle over a

certain time interval. The difference between the particle’s initial and final positions

Net motion of particles causes the vibrationIdeally, net motion is zero once vibration has

stopped. Therefore no work is done and no energy is lost by the vibration

Page 7: All matter is made of _______________ Particles are constantly ______________ As temperature increases, particles move __________ As temperature increases,

Particle Behaviour in Different MediaAll vibrations need a medium to transfer the waves.

A medium’s effectiveness at transmitting vibrations depends on its molecular and mechanical structure density temperature

Speed and distance a wave can travel depends on the composition of the medium. more rigid = faster waves that travel fartherless rigid = disperse more energy thus reducing speed and distance

Page 8: All matter is made of _______________ Particles are constantly ______________ As temperature increases, particles move __________ As temperature increases,

Particle Behaviour in Different Media

SolidsAtoms held together in crystal formation so

they can only vibrate slightlyElastic: medium returns to its original shape

after being disturbedMost solids have this property

Rigid materials transfer energy more efficiently than non-rigid materials

Page 9: All matter is made of _______________ Particles are constantly ______________ As temperature increases, particles move __________ As temperature increases,

Particle Behaviour in Different MediaFluidsLiquid molecules are in contact, so they are

still very effective transmitters of wavesGases have the lowest particle density, so

they are the least effective wave transmittersGases rely on translational motion:

The straight-line motion of a molecule

Page 10: All matter is made of _______________ Particles are constantly ______________ As temperature increases, particles move __________ As temperature increases,

Types of Mechanical WavesTransverse Waves: particles vibrate

perpendicular to the direction of energy flow. Eg. Guitar string: energy flows down the string

but motion is back and forth from the finger/pick plucking the string

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Longitudinal Wave: particles vibrate parallel to the direction of energy flow.Eg. slinky

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Parts of a Longitudinal WaveCompressions: regions where particles in a

wave are close together (high pressure in gasses)

Rarefactions: regions where particles in a wave are further apart (low pressure in gasses)

Page 13: All matter is made of _______________ Particles are constantly ______________ As temperature increases, particles move __________ As temperature increases,

SoundLongitudinal waves produce sound:

Energy produced by rapidly vibrating objects that are detectable by the ear

Sound (and other forms of energy, too) is transmitted ONLY as a longitudinal wave in fluids, but can be either transverse or longitudinal in solids.

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What Type of Wave?A complex wave – combination of both types due to wind effects near the surface

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Wave CharacteristicsTime-based characteristics:

CycleOne complete vibration = one cycle

Frequency (f)Number of cycles per secondUnits: 1/s = hertz (Hz)

Period (T)Time required for one cycle

f = 1/T and T = 1/f

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Wave CharacteristicsAmplitude• Maximum distance from equilibrium

Wavelength (λ)Distance between midpoints of two crests, or midpoints of two troughs

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Wave CharacteristicsPhaseThe x-coordinate of a particleWhen the waveform has been shifted along

the x-axis, this is a phase shiftParticles are considered to be in phase

when:They have the same amplitudeThey are vibrating in the same directionThey have the same phase shift

SHOW WAVE INTERACTION IN MY NELSON

Page 18: All matter is made of _______________ Particles are constantly ______________ As temperature increases, particles move __________ As temperature increases,

HomeworkFrom textbook:

8.1 Practice Questions #1 - 5

8.2 Practice Questions # 1-6, 8

8.3 Practice Questions # 1, 4, 5