Lecture 6

Question 1

What is the angular velocity at a given latitude

Answer 1

-it is equal to the angular velocty times the square of the distance to the axis of its rotation

Question 2

Does angular velocity increases if one moves northward in the northern hemisphere

Answer 2

• yes
• > if one moves northward in the northern hemisphere, one is decreasing the distance to the pole
• > thus to conserve angular momentum. the angular velocity must increase
• > to increase the angular velocty, eastward acceleration must occur
• > thus the deflection is to the east

Question 3

What are waves

Answer 3

• waves are energy in motion
• > energy is being transmitted through cyclic motion in matter
• > the medium does not travel as the enrgy passes through
• > but particles oscillate in place as the energy passes through them

Question 4

Do all waves begin as disturbances

Answer 4

-yes

Question 5

What is a disturbing force

Answer 5

• it is the energy that causes ocean waves to form
• > eg; a rock thrown into a still pond creates waves that radiate out in all directions

-the most common is wind blowing across the ocean surface

Question 6

What are the four ways that waves are created in the ocean

Answer 6

1) Interactions of winds with the ocean surface
2) Impacts on the ocean

3) Tidal interactions
- >caused by the gravitational pull of the Moon and the Sun

4)Passage of vessel or mairine mammals

Question 7

What are the three different types of waves created with different densities

Answer 7

Air-ocean interface

• > movement of air across the ocean surface creates ocean waves(waves)
• > movement of air across creates atmospheric waves
• > movement of water across water creates internal waves

Question 8

Where do surface and internal waves occur

Answer 8

Surface waves
->they only occur in the uppermost part of the ocean

Internal waves
->occur within the ocean along the boundary between water masses of different densities

Question 9

Where are the largest waves in the world

Answer 9

-they are in the prevailing westerly wind belt in the Southern Hemisphere

Question 10

Does the ocean’s tropical regions have small wave heights

Answer 10

-yes

Question 11

What are internal waves associated with

Answer 11

• they are associated with a pycnocline
• > a pycnocline is a layer of rapidly changing density
• note internal waves are larger than surface waves
• > with heights exceeding 100 metres

Question 12

What are the three different ways that particles can move due to energy transmission by waves

Answer 12

1) Longitudinal
- >back and forth
- >move through all states

2) Up and down
- >transverse
- >only move through solids

3) Around and around
- >orbital
- >a combination of transverse and longitudinal
- >aka interface waves

Question 13

Do waves move matter in 3 dimensions

Answer 13

-yes

Question 14

What are progressive waves

Answer 14

• they are those where the waveform can be observed travelling through the medium
• > eg; longitidunal, transverse and orbital waves are all progressive waves

Question 15

What are the two competing forces that produce waves

Answer 15

Disturbing force

• > modified un-disturbed medium to create the wave
• > most common such force is the wind that blows over the surface and transfers energy to the ocean

Restoring force

• > this force tends to bring a system to its undisturbed state
• > for waves along liquid surfaces, the restoring force is gravity

Question 16

What is a crest and trough

Answer 16

Crest
->the point of highest elevation of a wave

Trough
->between each pair of crests

Question 17

What is a wave height, amplitude and wavelength

Answer 17

Wave height
->the vertical distance between the crest and the trough

Amplitude
->vertical distance between the crest or trough and mean water level

Wavelength
->the distance between each successive pair of crests or troughs

Question 18

What is the definition of a wave period and frequency

Answer 18

Period
->time for the wave to move a distance equal to one wavelength

Frequency
->the number of crests or troughs that pass a fixed point per unit of time

Question 19

What is the formula for the wave speed

Answer 19

• it is wavelength over the period
• > this is the rate the wave form moves at
• > not the water

Question 20

What is the formula for wave steepness

Answer 20

• ratio of wave height to the wavelength
• 1/7 ratio dictates the maximum height of a wave
• > a wave 7 metres long can only be 1 meter high
• > any higher and it would break

Question 21

Describe the circular orbit motion

Answer 21

• wave particles move in a circle
• > waveform travels forward
• > wave energy advances
• > individual particles that transmit the wave return essentially to the same place
• the object moves up and backward as the crest approach
• > the objects moves up and forward after the crest
• > down and forward after the crest

-the object moves down and backwards as the trough approaches

Question 22

What is the wave base

Answer 22

• depth below the surface at which the circular orbit becomes so small
• > that the movement is negligible
• > equal to half of the wavelength measured from the still water level at the top

-so the circular orbital motion decreases quickly below the surface

Question 23

What is a deep water wave

Answer 23

• if water depth is greater than wave base
• > wave is a deep water wave

-note deep-water waves have no interference with the ocean bottom

Question 24

What does deep water wave speed vary with

Answer 24

• it only varies with wavelength
• > the longer the wavelength, the faster the deep-water wave travels
• a fast wave doesn’t necessarily have a large wave height
• > because wave speed only depends on wavelength

Question 25

What are shallow-water waves

Answer 25

• if water depth is less than 1/20 of the wavelength
• > wave is a shallow ater wave or long wave
• shallow water waves are said to touch the bottom or feel the bottom
• > because they touch the ocean floor
• > which interferes with the wave’s orbital motion

Question 26

Does shallow-water waves include all wind-generated waves

Answer 26

• yes

- >it includes all wind-generated waves in the open ocean where water depths far exceed the wavebase

Question 27

Is shallow water wave speed determined by water depth

Answer 27

• yes and only water depth
• > so for shallow water waves, the deeper the water
• > the faster the wave travels

Question 28

Describe how waves are created

Answer 28

• first waves to form are capillary waves(ripples)
• > they are small rounded waves with V-shaped troughs and small(1.74 cm) wavelengths
• over time, water catched more wind
• > more energy is transferred to the ocean and gravity waves develop
• > symmetric waves with wavelengths greater than 1.74 cm
• > initially gravity wavees are longer than they are high