# Butler Middle School 8 th Grade Science Bob, Paul, Ms. Adams, Dec 4, 2012 Ocean Tides.

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Butler Middle School 8 th Grade Science Bob, Paul, Ms. Adams, Dec 4, 2012 Ocean Tides

2 At Low Tide there can be lots of Beach

33 At High Tide not so much

4 Ogunquit Beach, Maine 4

5 Low Tide High Tide

Bay of Fundy New Brunswick, Canada Butler Middle School

Merrimack River & Atlantic Ocean Butler Mid School Lowell, MA Lawrence Haverhill Newburyport Nashua

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 drive propellers connected to generators

12 Quiz #2: What question might a Scientist ask now?

What Causes High and Low Tides?

To explain Tides we need to understand Gravity Sir Issac Newton 1642-1727 English Scientist

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 mM D

Math form of Newton’s Gravity Law

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 High Tide High Tide Low Tide Low Tide High Tides occur on opposite sides of Earth Point A Moon pulls on water at Earth’s surface Water flows toward A Point B Moon pulls on entire Earth Leaving the water behind Points C & D Low tides occur between the two high tides

Spring and Neap Tides New Moon Spring Tide, higher than normal tide Full Moon Neap Tide, less difference between low & high tides 1 st 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

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