waves and vibrations. waves rogue wave definition of a wave
TRANSCRIPT
Waves and vibrations
Waves
Rogue wave
DEFINITION OF A WAVE
What is a wave?
• Is a disturbance that carries energy through matter or space
• It may or may not need a medium to move through, depending on the type of wave
Does a floating object move with the ripple?
Response
• Though the object will move as the ripple moves underneath, the extent of motion is much less than the wave it self
DEFINITION OF A MEDIUM
Medium
Is any material through which a wave passes through
Mediums move only a small amount compared to the distance the wave travels
In general the medium returns to its original position, after the energy of the wave has passed
WHAT IS A VIBRATION?
An object vibrates when every portion of object repeats its motion
along a simple path over a measurable length of time
Vibrations
• Involve transformations of energy• Potential to Kinetic and back
• Think of a weight on the spring
Cause of a vibration
• Repeated application of forces on an object or medium
Another name for this type of motion is…
• Periodic Motion
• Any motion that repeats in a regular cycle
WAVES AND ENERGY
Waves transfer energy
• We know waves transfer energy because they do Work
• Water waves boat, leaf, surfer…• Sound waves eardrum• Light waves on your eye, photographic film
Have you ever been hit by an ocean wave?
• Then you can get the idea that ocean waves can carry a lot of energy.
• Research is underway to find ways to harness energy of ocean waves
• Some of this research is being done at the university of Delaware
Energy from Ocean Waves
• June 2007
Wave Energy Bill Approved by U.S. House Science Committee
Washington, DC [RenewableEnergyAccess.com]
The U.S. House of Representatives Science and Technology Committee has approved, by voice vote, renewable energy legislation that would invest approximately $200 million in federal
funds to advance research and development of wave energy technologies over the next four
years.
Tsunamis
• Huge ocean wave caused by massive displacement of water
WHAT IS PERIODIC MOTION ?Simple Harmonic motion
Periodic motion is broadly defined
• Includes items moving in circles
• More interested in subsection that deals back and forth motion
• Simple harmonic motion
SIMPLE HARMONIC MOTION
Simple harmonic motion• Examples: Slinky, swings, Bungee divers (hopefully)
• Object starts at equilibrium (balanced forces)
• As object is pulled away from equilibrium, the force trying to bring it back (restorative) increases
• Restorative force is directly proportional to displacement from equilibrium point
• Motion is periodic and repetitive
Damped Harmonic Motion
• The up and down motion fades over time
• Result of Friction, Air resistance or internal mechanisms
• Can be advantageous
TYPES OF WAVES
Mechanical Waves
• Waves that need a medium to move through
• A mechanical wave is a series of energy pulses that pass through matter
• Any vibration in matter is the source of a mechanical wave.
Examples of mechanical waves:
• Sound• Water wave• earthquake
DIFFERENT MECHANICAL WAVES MOTION
Mechanical waves
Transverse wave Longitudinal wave
Transverse waves
• Waves in which the motion of the particles is perpendicular to the motion of the wave (energy)
• Vibration is perpendicular in direction to motion of energy
• The “wave” that travels around a stadium
Demo of transverse waves
Longitudinal waves
• Direction of force is parallel to direction of pulse
• Direction of vibration is parallel to direction of energy
• Compression and rarification in medium
• Example: Sound
Rarification
• A region in a medium where the density of matter is decreased
• Medium is stretched or thinned
WHAT DOES THE SECTION OF SLINKY WANT TO DO AS YOU COMPRESS IT?
Answer
• The rest of the slinky pulls back, until it reaches the equilibrium point
• If the slinky section overshoots, it will be pulled back in the other direction
• Simple harmonic motion
Surface waves
• Occur at boundaries between two different medium
• Combination of the two
• Particles in the medium roll or take a circular path
• Example: Ocean waves, Surface wave of an earthquake
What are the types of waves that do not need a medium to move ?
ELECTROMAGNETIC WAVES
Electromagnetic waves• Light travels through space which does not contain
matter in all places
• An electromagnetic wave does not need a medium to pass through a space.
• Additional examples of electromagnetic waves, x-rays, microwaves, ultraviolet light, infrared radiation, gamma rays…
• More about these when we discuss light
Difference in waves
• Related to the different ways that energy is transferred.
• Mechanical waves require a mechanical force to transfer the energy (things bumping into each other)
• The energy from Electromagnetic waves is absorbed by a atom and then readmitted
Difference in speed
• Electromagnetic are much faster
• As the medium gets denser, mechanical waves tend to get faster, electromagnetic waves tend to slow down