TOPIC: EnergyAIM: Describe waves.

Do Now: (Take out your waves reading notes)

Review Question #1 on back of KE and PE reading notes

HW: CL Energy due Monday!

If both of these balls are traveling down a bowling lane at the SAME speed, which one would have more kinetic energy? Support your answer.

Wave •Traveling disturbance that carries energy from one place to another

•REPEATING disturbance

A pebble tossed into the water will create a circular disturbance which travels outwards in all directions. The pebble transfers some of its energy to nearby water molecules causing them to move. These water molecules transfer this energy to molecules around them…Energy is traveling in the form of a wave on the surface of the water.

There is a great amount of energy in these waves hitting the shore.

Cause of waves =

VIBRATIONS

Slinky waves can be made by vibrating the coil back & forth in either a horizontal or a vertical direction.

A tuning fork forces air particles to vibrate creating

sound.

A wave is the movement of energy from a vibrating source.

Matter waves travel through:MEDIUM

Medium for the following waves:–Ocean waves =

water

–Sound waves = air

Mechanical

waves

•Require a medium • Ex: Sound waves• Sound can’t be heard

in outer space • Why???

–Bc outer space is a vacuum

The sound produced by the bell cannot be heard since sound can’t travel through a vacuum. It is a mechanical wave.

•Medium not needed –CAN TRAVEL THROUGH A VACUUM (no matter exists)

•Ex : light & radio waves, x-rays

Electromagnetic

waves

Vacuum•Region where no matter exists

•Example: outer space

Normal resting position

Crest

Trough

•Crest – high points

•Trough – lowest points

Amplitude

•Amplitude – height–Distance from crest/trough to rest

–High amp = a lot of energy

•Wavelength – distance bw 2 crests or 2 troughs

Wavelength

Wavelength

Frequency

•# of complete waves per unit of time

Can you see the difference between these two waves? Hint…look at the movement of the particles.

Transverse Waves

Direction of particles

Direction of wave

•Particles of medium move at RIGHT ANGLES to direction of the wave

(PERPENDICULAR)

•Ex: Ocean Waves, waves on a rope

Longitudinal waves(Compressional waves)

Direction of wave

Direction of particles (left & right)

•Particles of medium move PARALLEL to the direction of the wave

(BACK AND FORTH)

Parts of a longitudinal wave

rarefaction

compression

•compression = where particles are close together

•rarefaction = where particles are far apart

rarefaction

compression

•Ex: Sound waves

Forces in Earth’s crust can cause regions of the crust to shift, bend, or even break. The breaking crust vibrates, creating seismic waves that carry energy outward. Seismic waves are a combination of compressional and transverse waves. They can travel through Earth and along Earth’s surface. The more the crust moves during an earthquake, the more energy is released.

Let’s summarize…

1.What is a wave?

2.Describe the cause of waves.

3.Describe a medium.

4.Identify an example of a medium.

5.Describe a vacuum.

6.How do particles move through a medium?

7.Explain the difference between mechanical and electromagnetic waves.

8.Explain the difference between transverse and longitudinal waves.

Any substance through which a wave can travel is called a

1.solid 

2.vacuum   

3.medium 

4.liquid

Waves transfer

1.energy

2.matter

3.particles

4.heat

Which of the following is the best example of a wave?

1.A stone rolling downhill

2.A vehicle moving on a bumpy road

3.A string vibrating on a guitar

4.A grasshopper jumping up and down

Which of the following statements applies to longitudinal waves?

1.The motion of the medium is random.

2.The motion of the medium is in a circular pattern.

3.The motion of the medium is parallel to the motion of the wave.

4.The motion of the medium is perpendicular to the motion of the wave.

Sound reaches our ears because sound makes particles

1.heat up.

2.slow down.

3.cool down.

4.vibrate.

The distance between the Earth and the moon was determined by measuring the time it took for light waves from the Earth to travel to the moon and back. Why was it not possible to use sound waves for this experiment?

1.Sound waves must move through a substance.

2.Sound waves change frequency on the return to earth.

3.Sound waves move too slowly for this technique to be accurate.

4.Sound waves move more slowly in the Earth’s atmosphere than in space.

A large spring is stretched horizontally between 2 people. One person wiggles the spring up and down at one end. The up-and-down vibration then moves along the spring on to the other person. Which of the following type of wave is created in the spring?

1.pressure wave

2.longitudinal wave

3.transverse wave

4.nonmechanical wave