Energy - the ability to do work or cause change. 1 point

Transcription

1 Energy and Waves

2 Energy - the ability to do work or cause change

3 Work - the transfer of energy Work = Force X Distance

4 Power - the rate at which work is done Power = Work Time

5 Kinetic Energy - the energy an object has due to its motion (kinetos = moving)

6 Kinetic energy depends on an object s mass and velocity

7 Potential Energy - stored energy that results from the position or shape of an object examples: stretched rubber band, water at top of waterfall, yo-yo, etc

8 Gravitational Potential Energy - potential energy related to an object s height an object s GPE increases with its weight and height

9 Elastic Potential Energy - energy of stretched or compressed objects Bow and arrow, spring, slingshot*, etc.

10 Law of Conservation of Energy - energy is not created or destroyed when one form of energy is transformed to another, no energy is destroyed in the process

11 Forms of Energy Mechanical Energy - energy associated with the position and motion of an object potential energy + kinetic energy the ability to do work

12 Thermal Energy - the total potential and kinetic energy of all of the particles in an object Heat energy warmer = more kinetic energy

13 Thermal energy is transferred by Conduction - from one particle of matter to another Convection - by movement of currents within a fluid Radiation - by electromagnetic waves (does not require matter; sunlight through empty space) (DRAW THIS DIAGRAM) 4 points

14 Electrical Energy - the energy of electrical charges kinetic energy if it is moving, potential energy if it is stored examples: electric current, batteries, lightning

15 Chemical Energy - potential energy stored in the bonds that hold chemical compounds together released when chemical bonds are broken examples: food, matches, coal

16 Nuclear Energy - energy stored in the nucleus of an atom

17 nuclear fission - nucleus is split in two, releasing energy nuclear fusion - fusing of two nuclei to form one larger atom; how the sun makes its energy* 2 points

18 Electromagnetic Energy - energy of light and other forms of radiation; transferred in waves examples: microwaves, x-rays, ultraviolet rays, infrared rays, radio waves, visible light

19 Energy Transfer Demonstrations Newton s cradle (conservation of momentum) Ball tower (kinetic energy depends on mass and velocity) Gauss gun (conservation of momentum) Bimetallic discs (potential energy) Ice melting discs (conductor vs insulator) Plasma ball (electrical energy to light energy) Light tube Sound ball Music

20 Wave - a disturbance that transfers energy from place to place

21 Most waves need something to travel through; the material through which a wave travels is called a medium a medium can be a solid, a liquid, or a gas

22 Mechanical Waves - require a medium Electromagnetic Waves - don t require a medium; can travel through empty space

23 A mechanical wave does not carry the medium with it transfers energy from one particle to the next (the particles bump into each other passing the wave s energy along) produced when a source of energy causes a medium to vibrate 2 points

24 Two types of mechanical waves Transverse waves - a wave that moves the medium in a direction perpendicular to the direction in which the wave travels High point = crest Low point = trough 2 points

25 Longitudinal waves - a wave that moves the medium in a direction parallel to the direction in which the wave travels Particles close together = compression Particles far apart = rarefaction 2 points

26 Four properties of waves - wavelength, amplitude, frequency, speed

27 Wavelength - distance between identical points on consecutive waves

28 Amplitude - distance between origin and crest (or trough) Greater amplitude = more energy

29 Frequency - number of waves that pass a point per unit time measured in hertz (Hz); waves per second

30 Speed - wavelength x frequency Light travels faster than sound, so you see lightning before you hear thunder

31 Interactions between waves Reflection - bouncing back of an object or a wave when it hits a surface through which it cannot pass

32 Refraction - the bending of waves as they enter a new medium at an angle

33 Diffraction - the bending of waves as they move around a barrier or pass through an opening

34 Interference - the interaction between waves that meet Constructive: waves combine to make a wave with a larger amplitude Destructive: waves combine to make a wave with a smaller amplitude 3 points

35 Standing wave - a wave that appears to stand in one place; really two waves interfering as they pass through each other

36 Resonance - increase in the amplitude of a vibration that occurs when external vibrations match an object s natural frequency

37 Sound - a disturbance that travels through a medium as a longitudinal wave begins as vibration

38 sound tends to travel fastest through solids, then liquids, then gases speed depends on elasticity, density, and temperature can t travel through a vacuum 2 points

39 sound travels through dry air at 343 m/s (767 mph) at 20 C (68 F) breaking the sound barrier (Chuck Yeager, 1947)

40 Loudness depends on energy of source and distance from source unit for loudness is the decibel (db)

41 Pitch depends on frequency Humans can hear sounds ranging from 20 Hz to 20,000 Hz (bass = 80 Hz, soprano = 1,000 Hz)

42 Electromagnetic wave - transverse wave that transfers electrical and magnetic energy EM radiation can travel through a vacuum moves through space at the speed of light

43 Electromagnetic spectrum - radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays Shorter wavelengths = higher energy

44 Visible light: ROY G. BIV

45 the color you see is reflected; all other colors are absorbed white objects reflect all of the colors and black objects absorb all colors

46 54 points possible