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

1. Ocean Tides Butler Middle School8th Grade ScienceBob, Paul, Ms. Adams, Dec 4, 2012

2. At Low Tide there can be lots of Beach

3. At High Tide not so much 3

4. Ogunquit Beach, Maine 4

5. High Tide Low Tide 5

6. Bay of FundyNew Brunswick, Canada Butler Middle School

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

9. 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

11. Tidal Energy • Tides move huge amounts of water each day • Getting control of it can produce a lot of energy Similar to wind power, tides can drive propellers connected to generators Largest Tidal Power Station is in France

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

13. What Causes High and Low Tides?

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

15. m M 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 D

16. Math form of Newton’s Gravity Law

17. 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

18. 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

19. A Closer look at High & Low Tides Low Tide High Tide High Tides occur on opposite sides of Earth Point A Moon pulls on water at Earth’s surfaceWater 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 High Tide Low Tide

20. Spring and Neap Tides Spring Tide, higher than normal tide New Moon Full Moon Neap Tide, less difference between low & high tides 1st quarter 90º 3rd quarter

21. 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

22. Tides Link to GravityTides 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