ATSC 113 Sail Module A Exam Questions
with Correct Answers
Wind velocity - Answer-- Speed of wind
- Increase in wind velocity increases wave size
Fetch - Answer-- Distance over the water that the wind can blow uninterrupted
- Increase in fetch increases wave size
Duration - Answer-- The amount of time the wind blows over a patch of water
- Increase in duration increases wave size
Factors affecting wave formation - Answer-1. Wind velocity
2. Fetch
3. Duration
The greater the wind velocity, the longer the fetch and the greater duration the wind
blows.
Travelling fetch - Answer-More than 1000nm
Drag - Answer-Force that acts against the relative motion . of one fluid with respect to
another fluid
Crest - Answer-Highest point of a wave
Trough - Answer-Lowest point of a wave
Wavelength - Answer-Distance from one crest/trough to the next (m)
Wave height - Answer-Height from trough to crest (m)
Wave steepness - Answer-ratio of wave height to wavelength
Amplitude - Answer-Distance from midpoint to bottom of trough (m)
Wave period - Answer-time for one full wavelength ot pass a given point (s)
Confused sea - Answer-Waves propagating from centre of a storm and combining with
existing waves create a confused sea with large and small waves of varying
wavelengths moving in all directions
Wave train - Answer-Waves disperse from storm and settle into groups of different wave
sizes and velocities continuously moving away from the source
, Group velocity - Answer-speed at which one group of waves travels across the water
Phase velocity - Answer-Speed of each wave in the group
Wind generated waves - Answer-1. Capillary waves
2. Gravity waves
Capillary waves (ripples) - Answer-- Small winds displace small amounts of water on the
surface, creating very short wavelength waves
- capillarity acts as the restoring force
- only a few cm in length
Gravity waves - Answer-Larger winds create gravity waves, gravity acts as restoring
force, can be metres to km long
swell - Answer-- Waves that arrive from distant storms
- gravity waves originating from heavy winds capable of traveling long distances across
the ocean with little loss of energy
Great circle routes/paths - Answer-Shortest distance across earth's surface taken by
swell to travel
Rogue waves - Answer-Very large waves that form due to wave constructive
interference
destructive inference - Answer-If the crest of one wave passes through the trough of
another, they cancel out
- resulting wave is smaller and carries less energy
constructive interference - Answer-if the crest of one wave passes through with the
crest of another wave, they add up
- resulting wave is bigger, carries higher energy, but is temporary
Tsunamis - Answer-very long wavelength waves resulting from seismic events
Types of breaking waves - Answer-spilling, plunging, surging
Spilling breakers - Answer-- Waves traveling across a gently sloping bottom
- The wave breaks long and slow
Plunging breakers - Answer-- waves approach moderate to steep bottoms
- wave becomes steeper than a spilling breakers and the crest falls as a well-defined
curl
with Correct Answers
Wind velocity - Answer-- Speed of wind
- Increase in wind velocity increases wave size
Fetch - Answer-- Distance over the water that the wind can blow uninterrupted
- Increase in fetch increases wave size
Duration - Answer-- The amount of time the wind blows over a patch of water
- Increase in duration increases wave size
Factors affecting wave formation - Answer-1. Wind velocity
2. Fetch
3. Duration
The greater the wind velocity, the longer the fetch and the greater duration the wind
blows.
Travelling fetch - Answer-More than 1000nm
Drag - Answer-Force that acts against the relative motion . of one fluid with respect to
another fluid
Crest - Answer-Highest point of a wave
Trough - Answer-Lowest point of a wave
Wavelength - Answer-Distance from one crest/trough to the next (m)
Wave height - Answer-Height from trough to crest (m)
Wave steepness - Answer-ratio of wave height to wavelength
Amplitude - Answer-Distance from midpoint to bottom of trough (m)
Wave period - Answer-time for one full wavelength ot pass a given point (s)
Confused sea - Answer-Waves propagating from centre of a storm and combining with
existing waves create a confused sea with large and small waves of varying
wavelengths moving in all directions
Wave train - Answer-Waves disperse from storm and settle into groups of different wave
sizes and velocities continuously moving away from the source
, Group velocity - Answer-speed at which one group of waves travels across the water
Phase velocity - Answer-Speed of each wave in the group
Wind generated waves - Answer-1. Capillary waves
2. Gravity waves
Capillary waves (ripples) - Answer-- Small winds displace small amounts of water on the
surface, creating very short wavelength waves
- capillarity acts as the restoring force
- only a few cm in length
Gravity waves - Answer-Larger winds create gravity waves, gravity acts as restoring
force, can be metres to km long
swell - Answer-- Waves that arrive from distant storms
- gravity waves originating from heavy winds capable of traveling long distances across
the ocean with little loss of energy
Great circle routes/paths - Answer-Shortest distance across earth's surface taken by
swell to travel
Rogue waves - Answer-Very large waves that form due to wave constructive
interference
destructive inference - Answer-If the crest of one wave passes through the trough of
another, they cancel out
- resulting wave is smaller and carries less energy
constructive interference - Answer-if the crest of one wave passes through with the
crest of another wave, they add up
- resulting wave is bigger, carries higher energy, but is temporary
Tsunamis - Answer-very long wavelength waves resulting from seismic events
Types of breaking waves - Answer-spilling, plunging, surging
Spilling breakers - Answer-- Waves traveling across a gently sloping bottom
- The wave breaks long and slow
Plunging breakers - Answer-- waves approach moderate to steep bottoms
- wave becomes steeper than a spilling breakers and the crest falls as a well-defined
curl
