Applied Science - Physics (6A) Pre Lab
 OBJECTIVES: Investigating matter and its interactions.  Comparing the four fundamental interactions. VOCABULARY: electromagnetic force gravity interaction strong nuclear weak nuclear MATERIALS: worksheet Students use the scientific method.

BACKGROUND:

Are you really at rest, when you sit down? When sometimes dies, do the atoms and molecules that make up that organism stop moving? Can you ever stop the spinning of a proton, neutron, or electron? Does our galaxy hang in the universe with no motion? The answer to these questions are all "no". Motion including spinning, velocity, acceleration, momentum and other terms, reflect this movement that all substances, large and small, are experiencing all the time. It is this motion that physicists must understand in order to explain physical phenomena. Motion can be accomplished by physical or electromagnetic waves. The study of motion is traditionally thought of as "mechanics". It is from all these motions that energy is emitted. Energy is created when matter moves, and since all substances are moving, energy is always being made even when an object is at rest. Terms like heat, solar, light, and sound refer to different forms of energy.

Observing and then describing nature is difficult. Precise definitions are needed. If the observations create a pattern, scientists can develop a mathematical formulation, that would help predict results. Other scientists, then attempt to observe and verify the prediction, through experimentation. As each prediction is verified, an understanding of the physical world slowly evolves.

Objects interact with each other. Many books refer to fundamental forces in the Universe. However, the word "force" is a very common term that means many things to students. In our terminology we will refer to interactions. There are four known interactions that seem to "rule" how all substances react. These include:

1. GRAVITY. An interaction that is a mutual attraction between masses is called gravity. Any two particles of matter attract one another with a force related to their mass and distance between the masses. Drop a ball or pencil. Ask the students what causes them to fall down? Gravity attracts objects to the ground.

2. ELECTROMAGNETIC. Use examples of light, electricity, and magnetism to show electromagnetic interactions. They will hopefully remember this from the 5th grade curriculum. Many other forces we encounter in everyday life, like friction or tension in a rope are physical waves and not electromagnetic. Electromagnetic forces arise from interactions of charged particles.

3. WEAK NUCLEAR. The interaction that holds atoms to other atoms including how compounds are held together.

4. STRONG NUCLEAR. The interaction that holds atoms together. Fission and fusion of subatomic particles are the processes by which these interaction can be released as useable energy.

In the Integrating Science, Math, and Technology program we use the commonly accepted four fundamental interactions: gravitational, electromagnetic, strong nuclear, and weak nuclear. Please recognize that these may change as scientists collect more data on how matter interacts. These interactions try to explain how matter lives in harmony with one another. Each of these interactions has their own method of producing energy, motion, and heat. When looking at the entire Universe, gravity is considered the weakest interaction, electromagnetism, weak atomic, and strong atomic increasing in strength respectively.

Gravitation is predictable in that we can calculate how objects will react in a gravitational world. Mathematical formulas model the consequences exquisitely. It is the weakest of the interaction, yet it is the interaction that has created the universe. Scientists do not know if gravitation moves in waves, or in discrete units as the other 3 interactions occur. Is gravity matter and how does it react? Does gravity bend space and time, and how did it create such a chaotic Universe? Sir Isaac Newton’s mathematical formulation of gravitational interaction is still used today. He stated that gravity increases in proportion to the product of any two masses and decreases in relation to the square of the distance between them. Einstein reformulated the gravitational concept to show that space and time become warped within a gravitational field (general theory of relativity). All the consequences of relativity are still being verified. For instance, inertia and gravity (if you look at the movement within the universe) can be seen as equivalent. Gravity holds us to the Earth, but if a person was in a box, and accelerated up, the person would fall to the floor and remain there as long as the enclosed box continued to accelerate. Most of the answers in understanding the nature of gravity are experiments that will involve far reaches of the Universe.

Many physicists feel that the three interactions of electromagnetism, weak, and strong all have a common mechanism. The structure of matter is affected by these interactions, acting inside of the nucleus (neutrons and protons) and electrons. Actually, the structure of matter includes other particles such as muon, pion, kaon, sigma and several hundred more. Protons and neutrons emit quarks and electrons emit leptons. There are four types of quarks. The up, the down, strange, and charm quarks can be emitted during decay. These quarks and leptons all decay into particles called gauge bosoms. Electromagnetism emits photons from their quarks and leptons. Weak emits "W" and "Z" bosoms from their quarks and leptons, and strong emits particles called color gluon from their quarks and leptons. All these gauge bosoms share a common mathematical description and similar physical behavior. Confusing, yes! The concepts however aren't confusing, electrons, protons, and neutrons are the basic ingredients of matter, and the other particles are for "flavoring."

The interaction termed electromagnetism is the net electrical charge of particles which is conserved throughout any reaction. All chemistry and hence all biology is a direct consequence of electromagnetic interaction of atoms and molecules.

The weak nuclear interaction was recognized with the discovery of radioactive decay by Henri Becquerel in 1896. Particles easily "escape" from the atomic structure over time. The energy of the original particles is conserved with new particles called neutrino or sometimes antineutrinos.

Strong nuclear interactions act on particles called hadrons which include protons, neutrons, pion, mesons, and baryons. This interaction is one of the strongest per unit of space known.

PROCEDURE:

1. You may want to introduce each of these interactions discussed above by demonstrating them. These interactions have their own type of motion that may be particular to that force. Within each of these major interactions make reference to different forces.

2. Give students the worksheet as a classroom discussion or homework assignment. The worksheet for the students should help them to begin classifying events that they see everyday.