Energy and Waves

• Energy - the ability to do work or cause change

1 point

• Work - the transfer of energy

• Work = Force X Distance

1 point

• Power - the rate at which work is done

• Power = Work

Time

1 point

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

1 point

• Kinetic energy depends on an object’s mass and velocity

1 point

• 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 Energy -energy stored in the nucleus of an atom

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

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

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

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

1 point

• Wavelength - distance between identical points on consecutive waves

1 point

• 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

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

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

• Visible light: ROY G. BIV

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

54 points possible