Energy and Waves -...
-
Upload
duongtuyen -
Category
Documents
-
view
216 -
download
1
Transcript of Energy and Waves -...
• 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
1 point
• Gravitational Potential Energy - potential energy related to an object’s height
• an object’s GPE increases with its weight and height
1 point
• Elastic Potential Energy - energy of stretched or compressed objects
• Bow and arrow, spring, slingshot*, etc.
1 point
• 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
1 point
• Forms of Energy
• Mechanical Energy - energy associated with the position and motion of an object
• potential energy + kinetic energy
• the ability to do work
1 point
• Thermal Energy - the total potential and kinetic energy of all of the particles in an object
• Heat energy
• warmer = more kinetic energy
1 point
• 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
1 point
• Chemical Energy - potential energy stored in the bonds that hold chemical compounds together
• released when chemical bonds are broken
• examples: food, matches, coal
1 point
• 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
1 point
• 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
1 point
• 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
1 point
• Mechanical Waves - require a medium
• Electromagnetic Waves - don’t require a medium; can travel through empty space
1 point
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
• Amplitude - distance between origin and crest (or trough)
• Greater amplitude = more energy
1 point
• Frequency - number of waves that pass a point per unit time
• measured in hertz (Hz); waves per second
1 point
• Speed - wavelength x frequency
• Light travels faster than sound, so you see lightning before you hear thunder
1 point
Interactions between waves
• Reflection - bouncing back of an object or a wave when it hits a surface through which it cannot pass
1 point
• Diffraction - the bending of waves as they move around a barrier or pass through an opening
1 point
• 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
1 point
• Resonance -increase in the amplitude of a vibration that occurs when external vibrations match an object’s natural frequency
1 point
• Sound - a disturbance that travels through a medium as a longitudinal wave
• begins as vibration
1 point
• 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)
1 point
• Loudness depends on energy of source and distance from source
• unit for loudness is the decibel (dB)
1 point
• Pitch depends on frequency
• Humans can hear sounds ranging from 20 Hz to 20,000 Hz (bass = 80 Hz, soprano = 1,000 Hz)
1 point
• 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
1 point
• Electromagnetic spectrum - radio waves, microwaves, infrared , visible light, ultraviolet, X-rays, and gamma rays
• Shorter wavelengths = higher energy
1 point
• the color you see is reflected; all other colors are absorbed
• white objects reflect all of the colors and black objects absorb all colors
1 point