The purpose of this unit is to present some basic principles of physical science to third grade students. I believe that the unit will also be of use to teachers of grades two thru five. The idea for the unit is an outgrowth of having done a previous unit about natural disasters. My original interest in natural disasters as a topic for teaching came from my observation that my students seemed to have a natural fascination with earthquakes, volcanoes, and other disasters. Of a more practical nature, physics is one branch of science that is not readily taught in elementary school and I was interested in learning more.
The basic principles I hope to cover are contained in Newton’s second and third laws. The second law states that acceleration of an object at rest is produced when a force acts on the mass of that object. The greater the mass of the object being accelerated the greater amount of force is needed to accelerate the object. Thus, an object won’t move until some force pushes it and the amount of force needed to move it depends on its size. The third law states that for every action there is an equal and opposite re-action. According to this when one object pushes another object it gets pushed back with equal force only in the opposite direction (Wiggins, pg. 41-42).
In order to convey this to students the unit focuses on four natural occurrences: landslides and avalanches, earthquakes, and volcanoes. The unit consists of a number of demonstrations simulating aspects of the natural occurrences mentioned with the aim of working backward to figure out how they occurred. While I have been putting the unit together, I have also been teaching aspects of the unit to my class. It has become apparent to me that they will need a lot of visuals and hands on activities.
The overarching purpose of this unit is to have students see that these occurrences are usually the result of some failure of nature. A landslide is the result of the failure of a slope of dirt to withstand the force of gravity. A similar thing happens in an avalanche only the failure is of a slope of snow. The eruption of a volcano is the result of the increasing pressure of the rising magma to fracture the rock above it allowing the magma to escape. Likewise, an earthquake occurs because of the failure of the tectonic plates to avoid collisions. Those earthquakes that are the result of divergent or pull-apart motion are the result of rocks failing (cracking) as a result of the tension placed upon them. Earthquakes resulting from a tranform fault or slide-past motion are the result of the uneven sides of the plates retarding their own movement and resulting in the release of large amounts of energy. Those earthquakes that are most destructive are those that occur at subduction zones where plates are colliding into one another and one is forced down under the other.