Butler Middle School 8 th Grade Science Bob, Paul, Ms. Adams, Dec 4, 2012 Ocean Tides
Dec 11, 2015
High and Low Tides
• 2 high tides and 2 low tides within every 24 hour day
• High & Low tides don’t occur at the same time every day
• Similarly, New & Full moons don’t occur on the same day each month
• The Changing tides can be used to produce energy
10
Quiz #1: What best describes all the previous
slides?(a) an experiment
(b) a procedure
(c) data and observations
(d) scientific method
(e) an advertisement for Ogunquit, Me
Tidal Energy
• Tides move huge amounts of water each day
• Getting control of it can produce a lot of energy
Largest Tidal Power Station is in France Similar to wind power, tides can drivepropellers connected to generators
Newton’s Universal Law of Gravitation
•All objects attract or pull on each other with an invisible force without contact
•The pull of gravity between 2 objects
depends on their masses and distance distance between them
•The bigger the objects the greater the attraction
•Gravity gets weaker as distance gets bigger
m MD
What Causes High and Low Tides?
• Answer is Complicated:– The Moon’s Gravity is mostly
responsible
– The Sun’s Gravity plays a smaller role because the sun is so far away compared to the Earth-Moon distance
– There are other reasons which you will learn about if you become a physicist or an astronomer
Gravity of Moon & Sun pull on Earth’s Oceans
Gravity keeps the moon in orbit around the earth
Gravity keeps the earth in orbit around the sun
A Closer look at High & Low Tides
HighTide
HighTide
LowTide
LowTide
High Tides occur on opposite sides of Earth
Point AMoon pulls on water at Earth’s surfaceWater flows toward A
Point BMoon pulls on entire EarthLeaving the water behind
Points C & DLow tides occur between the two high tides
Spring and Neap Tides
NewMoon
Spring Tide, higher than normal tide
FullMoon
Neap Tide, less difference between low & high tides1st quarter
3rd quarter
90º
Vocabulary• Range
– Difference between high and low tide
• Neap Tide– Occurs when Range is smallest– Sun, Earth, Moon form 90º angle
• Spring Tide– Occurs when Range is largest– Sun, Earth, Moon are aligned
• Ebb Tide– Water is moving away from shore
• Flood Tide– Water is moving toward shore
• Slack Tide– About 1 minute between water moving in then out– or the interval between Flood & Ebb tides
Tides Link to Gravity
Tides link to Gravity
• Ocean Tides on Earth are caused mainly by the pull of the Moon’s Gravity– Sun’s Gravity has a smaller effect
• Newton’s Universal Law of Gravitation– Force of Gravity is invisible
– All objects attract or pull on each other
– The force of gravity between 2 objects depends on their masses and distance between them
– The bigger the objects the greater the attraction
– Gravity gets weaker as distance gets bigger