16.9 Waves

16.9 Waves

  • The best way to transfer energy from the driving force into the oscillator is at resonance.
    • The suspension system of a car is not immune to resonance.
    • Even though finely engineered shock absorbers convert mechanical energy to thermal energy almost as fast as it comes in, speed bumps still cause a large-amplitude oscillation.
    • If you travel at the wrong speed on a gravel road, the bumps are very noticeable, whereas if you travel at the right speed, the bumps are not as noticeable.
    • The Millennium Bridge in London was closed for a short period of time due to an inspection.
  • The chest is an example of a system at resonance.
    • The system is highly efficient because it is critically damped.
  • The bridge in Washington state collapsed in 1940.
    • The bridge was hit by heavy cross winds.
  • The performer needs to be singing a note that matches the glass's natural frequencies.
    • The glass responds to a sound wave by replicating the sound wave's frequencies.
    • The glass begins to vibrate and shatter when enough energy is introduced into the system.
  • Waves in the ocean are the same as all other waves.
  • The familiar water wave is the most intuitive wave to imagine.
  • Water waves can be created by a rock thrown into a pond or a swimmer splashing the surface repeatedly.
    • The air pressure in the speaker may have caused the sound waves to change.
    • There are several types of earthquakes, including pressures under the surface and Earth's surface.
    • An analogy with water waves is how radio waves are most easily understood.
    • There is more to water waves than just a mental image.
    • Water waves have characteristics that are common to all waves.
    • A small set of underlying principles can be used to describe wave characteristics.
  • A wave is a movement from the place it was created.
    • The simplest waves are associated with simple motion.
    • The simplified water wave is an up and down disturbance of the water surface.
    • As the wave crests and troughs pass under the bird, it causes a sea gull to move up and down in a simple motion.
    • The wave's period is the time for one complete up and down motion.
    • The wave's Frequency is the same.
    • The wave moves to the right.
    • The wave is moving to the right, not the water itself, as the bird would move to the right.
  • propagation speed is also known as wave velocity, because the disturbance travels from one location to another.
  • Water waves push water from one direction to another.
    • The particles of water tend to stay in one place, because of the energy in the wave.
    • The water stays in one place as the energy moves through it.
    • If you feel pushed in the ocean, what you feel is the wave's energy, not a rush of water.
  • An idealized ocean wave passes under a sea gull that bobs up and down.
    • The wavelength is the distance between adjacent parts of the wave.
    • The surface moves parallel to the surface at a fast pace.
  • The distance the wave travels in a given time is the speed of propagation.
  • All types of waves are held together by this fundamental relationship.
    • For water waves, is the speed of a surface wave; for sound, is the speed of sound; and for visible light, is the speed of light.
  • Wait for the water to settle in a large bowl or basin so there are no ripples.
    • Put a cork in the middle of the bowl.
    • Estimate the wavelength and period of the water wave that travels away from the cork.
  • Wait for the water to settle and remove the cork from the bowl.
    • The cork should be dropped at a different height than the first drop.
  • We can find the wave velocity.
  • This slow speed is reasonable for an ocean wave.
    • The wave moves to the right in the figure at this speed, not the varying speed at which the sea gull moves up and down.
  • A simple wave is a periodic disturbance that travels from one place to another.
    • The speed of propagation does not affect the size of the disturbance.
  • In this example of a wave, the wave propagation is horizontal and the cord is vertical.
  • In this example of a longitudinal wave, the wave propagation is horizontal and the cord is in the opposite direction.
  • Waves can be a combination of the two.
    • There are waves on the strings of musical instruments.
  • Waves in the air and water are related.
    • Transient variations in pressure are transmitted in fluids.
    • The sound waves in fluids must be longitudinal or compressional because they don't have shear strength.
  • Longitudinal and transverse sound can be heard in a solid object.
  • The guitar string has a wave on it.
    • A sheet of paper rattles in a direction that shows the sound wave is longitudinal.
  • The compressional and shear components of earthquake waves under Earth's surface.
    • The components have important individual characteristics.
    • The surface waves on water are similar to the surface waves on earthquakes.
  • The motion of the wave can affect the propagation of energy in a different direction.
    • Understanding how different types of waves affect the materials around them is important.
  • A string is vibrating in slow motion.
    • If you want to make waves, jiggle the end of the string.
    • The end can be loosened or fixed.