Physics 2WAVES

ppt. by Robin D. Seamon

(Heat & Temperature Energy Waves)

•temperature: average kinetic Energy of particles in an object

Solid

Liquid

Gas

http://www.bcssa.org/newsroom/scholarships/great8sci/Matter/Choose_Matter.html

The more kinetic E the higher the temp.

Interactive LAB

•Thermometer: thin glass tube filled with mercury or alcohol

•Thermal expansion: temp goes up, volume goes up b/c particles spread out

examples: thermometer, hwy joints, bimetallic strips in thermostats

Kelvin Celcius Farenheit

373°K 100°C 212°F

310°K 37°C 98.6°F

273°K 0°C 32°F

Kelvin 0 = when all molecular motion stops

Thermostat:

•Conduit: conducts/ allows Energy transfer; water, metal

•Insulator: does not allow Energy transfer; fiberglass, cardboard, air, cork, wood, rubber, wood

•Heat: Energy transferred between objects at different temperatures; thermal EnergyIf two objects are connected, there is always transfer between high temp to low temp

•Thermal equilibrium Energy transfer until the same temperature on both

Put ‘C’ for Conductor & ‘I’ for Insulator.

Curling ironoven mittceramic bowliron skilletstove coilcookie sheetplastic spatulafiberglass insulationcopper pipe

•Conduction transfer of thermal energy through direct contact

•Convection transfer of thermal energy by movement of liquid/gas (hot up, cold down)

•Radiation transfer of thermal energy by electromagnetic waves (visible light & ultraviolet waves)

Which changes temperature faster: --air, water?

Can’t measure transferred E directly; must be calculated:

Heat (J) = specific heat x mass x change in temp

LAB: Feel the Heat

Trial Mass of nails (g) Volume of water that equals mass of nails (mL)

Initial temp. of water & nails

Initial temp of water to which nails will be transferred

Final temp of water and nails combined

1

2

Procedure:

• Bundle the nails together with a rubber band. Record the mass. Tie string around, leaving one end 15 cm long.

• Put bundle of nails into a cup, letting string dangle out. Fill the cup with hot water, covering nails. Set aside 5 min.

• Use graduated cylinder to measure enough cold water to exactly the mass of nails. Record.

• Measure & record the temp of the hot water with the nails & temp of cold water.

• Use string to transfer the bundle of nails to the cup of cold water. Use the thermometer to monitor the temperature of water-nail mixture. When the temp stops changing record this final temp.

• Empty cups, dry nails. Repeat for trial 2, but switch the hot & cold water. Record data.

Conclusion:

The cold water in Trial 1 gained energy. Where did the E come from?How does the E gained by the nails in Trial 2 compare with the E lost by the hot water in Trial 2? Which material seems to be able to hold E better… iron or water?

p. 430

Materials: balance, 2 cups, cylinder, 10 nails, string, rubber band, thermometer, hot water, cold water

WAVES

SCIENCE SONGS

•Wave: disturbance than transmits Energy through matter or empty space;

--as wave travels it does work on everything in its path

•Mechanical waves: need a mediumexamples- sound wave, ocean wave

•Some waves don’t need a mediumexamples- visible light, microwaves, tv, radio signals, x-rays

Compression waves pressed close together

Rarefraction waves stretched farther apart

Example: sound wave

Rarefraction

Waves:

Transverse wave- particles move up & down, perpendicular to direction wave is going

Longitudinal wave- particle move horizontally along the wave in the direction the wave is moving

Surface wave- combination of transverse & longitudinal wave

VIDEO: HSW Wavelength Basics

ADVANCE

Transverse wave- particles move up & down, perpendicular to direction wave is going

BACK

Longitudinal wave- particle move horizontally along the wave in the direction the wave is moving

BACK

Surface Waves

HSW: Waves of Destruction Surface Waves (3 min) BACK

Properties of Waves

•Amplitude: maximum distance the particles vibrate

•Wavelength: distance between two crests or compressions in a wave

•Frequency: number of waves in a given amount of time

•Wave speed: speed at which wave travels (v)

Wave Interactions

reflection- wave bounces back after hitting a barrier;examples: light reflected lets us see itsound echoes

refraction- bending of a wave as it passes from one medium to another at an angle (because wave changes speed in a different medium)example:light through a prism (light is dispersed into separate colors)

HSW: Exploring sound, Reverberation (3 min)

Diffraction bending of waves around a barrier

Interference two or move waves overlap

-constructive interference 2 waves overlap crests & troughs, combining both waves’ energy… makes it stronger!

-destructive interference 2 waves overlap one crest on one trough, cancels out each other’s Energy

HSW: Assignment Discovery: Sound/Interference (1 ½ min)

Ripple Tank Simulation

Standing waves: pattern looks like wave is standing still

Resonance: two objects naturally vibrate at the same frequency; sound of one causes the other to vibrate

VIDEO: Sound/Resonance-Shattering glass (15 min) United Streaming

LAB: Musical Instruments

SCIENCE SONGS

• HSW: Exploring Sound (23 min) not saved

• HSW: Exploring Light ( 3 min) not saved

• Physical Science: Light ( 20 min)

• Physical Science: Sound ( 20 min)