How Does the Moon Affect the Tides

How Does the Moon Affect the Tides

5th Grade/Unit 4: Position and Motion of Objects in the Sky

Goal:

a.  The students will be involved in a demonstration that teaches them how the moon affects the tides on earth.

b.  E.ST.05.25 Explain the tides of the oceans as they relate to the gravitational pull and orbit of the moon.

Background:

a.  Prior Knowledge:

The students should have an understanding of the moon. They need to know that the moon revolves around the Earth. The students should have an understanding of gravity and that the moon has less gravity than earth, but still has a significant amount of gravity.

b.  Reference Sources: Adapted from http://www.usc.edu/org/seagrant/Education/IELessons/Unit1/Lesson4/U1L4A.html

c.  Common Student Misconceptions:

d.  Timeframe of Activity: 30 minutes to 1 hour

Vocabulary:

Gravity – a constant pull exerted by all bodies. The larger the body the greater the force of gravity.

Materials:

a.  None

Procedure:

1.  Teacher should begin with a discussion of high and low tides.

2.  How many of you have been to the beach at high and low tides?

3.  What did you notice about the seashore?
(more rocks, area, and animals can be seen when the tide was 'out' or low, waves and water were further up on the beach when the tide was in or high)

4.  Ask for students ideas on what high and low tides are, and why they occur.

5.  Have the class form a circle in a large area. This could be in the classroom, on a lawn, or if necessary, on the playground.

6.  The ideal way for students to sit is crossed-legged with hands holding the next person's elbows to form a strong circle. If the class is reluctant to touch, have them kneel "knock-kneed" next to each other in a circle.

7.  One person is the moon and moves around the outside of the circle. The circle is the waters of the earth. As the moon passes behind the students (water), the waters bulge (lean) toward the moon, and then into the center as the moon passes. As the moon moves, have the students that are opposite the moon lean away from the moon (this represents water bulging out on the opposite side of the earth) and then have them lean into the center as the moon passes.

8.  Have the moon stop, and let the class see where the high tides are (next to the moon and at the opposite side of the circle). Then the moon continues to circle. Have the moon stop at several points in the circle and let the class see where the high and low tides are in relation to the orbit of the moon. (Low tide will be at the sides halfway between the high tide bulges.)

9.  The moon can then circle the earth several times so the rhythm of the passing of the moon and the bulging of the waters is experienced by the class.

Results and Conclusions:

As the moon travels around the circle, the students closest to the moon and farthest from the moon would lean away from the circle. The students on the sides that are neither towards nor away from the moon would be leaning in to the middle of the circle. The students leaning out would be high tide. The students leaning in would be low tide. As the moon moves around the circle, the location of the high and low tides change. The students should understand from this project that there are two high and low tides each day. These tides are on opposite sides of the globe. These tides are a reaction to the moon as it travels around the earth.