Energy and Waves
Energy - the ability to do work or cause change
Work - the transfer of energy Work = Force X Distance
Power - the rate at which work is done Power = Work Time
Kinetic Energy - the energy an object has due to its motion (kinetos = moving)
Kinetic energy depends on an object s mass and velocity
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
Gravitational Potential Energy - potential energy related to an object s height an object s GPE increases with its weight and height
Elastic Potential Energy - energy of stretched or compressed objects Bow and arrow, spring, slingshot*, etc.
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
Forms of Energy Mechanical Energy - energy associated with the position and motion of an object potential energy + kinetic energy the ability to do work
Thermal Energy - the total potential and kinetic energy of all of the particles in an object Heat energy warmer = more kinetic energy
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
Electrical Energy - the energy of electrical charges kinetic energy if it is moving, potential energy if it is stored examples: electric current, batteries, lightning
Chemical Energy - potential energy stored in the bonds that hold chemical compounds together released when chemical bonds are broken examples: food, matches, coal
Nuclear Energy - energy stored in the nucleus of an atom
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
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
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
Wave - a disturbance that transfers energy from place to place
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
Mechanical Waves - require a medium Electromagnetic Waves - don t require a medium; can travel through empty space
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
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
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
Four properties of waves - wavelength, amplitude, frequency, speed
Wavelength - distance between identical points on consecutive waves
Amplitude - distance between origin and crest (or trough) Greater amplitude = more energy
Frequency - number of waves that pass a point per unit time measured in hertz (Hz); waves per second
Speed - wavelength x frequency Light travels faster than sound, so you see lightning before you hear thunder
Interactions between waves Reflection - bouncing back of an object or a wave when it hits a surface through which it cannot pass
Refraction - the bending of waves as they enter a new medium at an angle
Diffraction - the bending of waves as they move around a barrier or pass through an opening
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
Standing wave - a wave that appears to stand in one place; really two waves interfering as they pass through each other
Resonance - increase in the amplitude of a vibration that occurs when external vibrations match an object s natural frequency
Sound - a disturbance that travels through a medium as a longitudinal wave begins as vibration
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
sound travels through dry air at 343 m/s (767 mph) at 20 C (68 F) breaking the sound barrier (Chuck Yeager, 1947)
Loudness depends on energy of source and distance from source unit for loudness is the decibel (db)
Pitch depends on frequency Humans can hear sounds ranging from 20 Hz to 20,000 Hz (bass = 80 Hz, soprano = 1,000 Hz)
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
Electromagnetic spectrum - radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays Shorter wavelengths = higher energy
Visible light: ROY G. BIV
the color you see is reflected; all other colors are absorbed white objects reflect all of the colors and black objects absorb all colors
54 points possible