Semester 1:

• Forces and Motion

• Forces at a Distance

• Conservation of Energy

Semester 2:

• Conservation of Energy

• Waves and Electromagnetic Radiation

• From the Nucleus to the Universe

Key Objectives:

Investigation 3:

• Expand the concepts developed in the previous storyline to include Newton's law of Universal Gravitation to explain the behavior of planets orbiting the sun and why they obey Kepler's three laws of orbital motion. Gravitation is always attractive between masses and an inverse square law. It is described by vectors.

Investigation 4:

• Electric charges are two kinds (+ & -). Likes repel, opposites attract. Charge differences can be caused by transfer during contact or temporarily induced by nearness w/o contact. The force between two point charges follows an inverse square law called Coulomb’s law. Electric forces are described by vectors. Gravitational forces are much smaller than electric forces. For example the electric force between a negatively charged electron and a positively charged proton in a hydrogen atom is 10^29 times larger than the gravitational force between their two masses. Graphic descriptions and calculations are similar to the mathematics used to describe gravity. Electric field and electric potential are useful ways to describe more complicated situations than point charges. Electric currents in circuits obey Ohm’s and Kirchoff’s laws. Calculations can be done applying these laws to parallel, series, and combined electric circuits.

Investigation 5

• Magnetic fields are caused by moving electrons AND changing magnetic fields can cause electrons to move. Students will be able to use the right hand rule and mathematics to calculate the strength and direction of fields created by permanent magnets and current carrying loops. They connect magnetic flux and electromotive force to induction and calculate the relationships represented by Biot-Savart’s and Faraday’s Laws. Electric current loops in spinning Earth at the boundary between the liquid and solid core generates the magnetic field around us that protects us from charged particle radiation from the solar wind. Throughout this investigation students will model systems and solve problems related to electromagnetic induction.

Key Objectives:

Investigation 9 Energy flow in both open and closed systems. Thermal energy on a microscopic scale is related to the total kinetic energy in a material, while the temperature is related to the average kinetic energy of the molecules in a material. Two objects of different temperature in contact transfer energy by conduction of motion from the fast molecules to the slow molecules. The transferring energy is called heat. The final temperature of both is in between the starting temperature. The three laws of thermal energy dynamics are Law 1: The best one could ever do is have energy in equal energy out, conservation of energy. Law 2: random motion always tends to increase over time so that some mechanical energy gets converted to thermal energy and you never get perfect conservation. The measure of increasing disorder is called entropy and it usually increases. Law 3: Increasing disorder slows down as the temperature approaches absolute zero (0°K). The Zeroth Law: Temperatures may approach absolute zero but can never get there. Compare temperature vs energy graphs will show they are not linear. The relationship between temperature, pressure and volume for gasses can be described by Boyle’s Law, Charles Law, and Guy-Lussac’s Law or they can be combined into the Ideal Gas Law. Specific heat describes how temperature in materials that are in the same phase respond to changes in thermal energy. Latent heat describes the heat necessary to change a material from one phase to another, liquid to gas for example, before the temperature will change. Heat is also transferred by convection and radiation. All three methods transfer heat from the hot core of the Earth into cold outer space. These processes, conduction from the core to the mantle, convection in the mantle breaking the crust into moving plates and radiation into space, drive plate tectonics. This results in seafloor spreading, mountain building, subduction zones, earthquakes at plate boundaries and volcanoes of various kinds on the surface of our planet.

From Investigation 4 we know electric charges are two kinds (+ & -). Likes repel, opposites attract. Charge differences can be caused by transfer during contact or temporarily induced by nearness w/o contact. The force between two point charges follows an inverse square law called Coulomb’s law. Electric forces are described by vectors. Gravitational forces are much smaller than electric forces. For example the electric force between a negatively charged electron and a positively charged proton in a hydrogen atom is 10^29 times larger than the gravitational force between their two masses. Graphic descriptions and calculations are similar to the mathematics used to describe gravity. Electric field and electric potential are useful ways to describe more complicated situations than point charges.

Electric force and electric potential energy equations can be made into very useful functions called electric field and electric potential. The electric field equation tells what force a complicated assembly of charges would have on a small charge at different distances from them. The electric potential equation tells what potential energy they would give the small charge at that spot. If you know the electric field and the electric potential it is much easier to predict what will happen than trying to grind through Coulomb's law for many charges. The electric field can also be represented as a picture. For example, the field around a positive charge is a plus sign with straight line arrows pointing out from it in all directions. The place where the lines are really close together the force is stronger and where they are far apart it is weaker.

A negative charge would have converging arrows.

Electric potential is very useful in explaining how batteries push electrons through wires. In circuits the difference in electric potential (V) between the positive and negative end of the battery pushes electrons in a wire. The metal the wire is made of determines how easily the electrons move. Resistance (R) is how these differences are described. The flowing electrons in the wires are called the current (I). Power is the rate at which electrical energy is used. The different devices in an electrical circuit can be in series or parallel. The way the current moves will differ depending on how the circuits are built. The main equations are Ohm’s Law V=I•R, the power law P = I^2 • R, or P

= I•V, also

Total resistance for series R = R1 + R2 + R3 etc and

Total resistance for parallel 1/R = 1/R1+ 1/R2 + 1/R3 ETC

Changing magnetic fields can move electrons in conductors. This electromagnetic induction can be used to make electric motors and also electric generators. Finally, how the spinning magnets in the generators are turned relates to our climate. If water or steam turns them, the way the steam is made has different impacts on global warming. Steam from geothermal hot water sources near volcanoes does not produce greenhouse gasses. Heat from burning methane, petroleum, or coal does. Heat from nuclear fission does not. Heat from concentrated sunlight does not.

Key Objectives:

From Investigation

The atomic model of matter is powerful and eventually leads to the periodic table of elements, which enables us to predict what will happen when atoms of elements interact. The negative electrons in clouds around the tiny and massive positively charged nucleus of an atom, which is made of positive protons and neutral neutrons (that hold it together); has its electrons in different energy levels associated with how many protons are in the nucleus. The electrons in the outermost energy level of one atom can interact with the outermost electrons of another atom resulting in forces between the atoms. This produces situations where the two atoms get close together and share pairs of electrons. This bonding is called “covalent bonding". In a different situation, one outer electron may be pulled from one atom to another. The element that lost the electron has a positive charge. The element that took the electron has a negative charge. The two atoms are pulled together by their opposite charges. This type of bonding is called “ionic bonding". A third possibility is that a large number of atoms of the same metal element, such as copper, are all together and the outer electrons slosh between identical atoms making the net positive inner parts somewhat like positive islands surrounded by a sea of electrons that keep them inside. This type of bonding is called "metallic bonding."

The nucleus of all atoms, except for the hydrogen with only one proton in its nucleus, is made of positive protons held together by neutral neutrons. Protons that close together have VERY strong electric force pushing them apart. The neutrons are mediators on the much larger strong nuclear force. Without that it would be impossible to have atoms more complex than one proton and one electron. Mass and energy are interchangeable as denoted by the famous equation E = MC^2. When you compare the mass of a helium atom’s nucleus to the total mass of the four particles that made it (2 protons and 2 neutrons), the nucleus doesn’t have as much mass as the total mass of its parts. Why? The missing mass was released as light energy during the formation of the nucleus. The apparent missing mass is called the mass deficit of the nucleus. When you look at the other elements’ nuclei iron has the highest mass deficit. This means that you can combine nuclei of the lighter elements up to iron and squeeze some energy out. This is nuclear fusion. On the other side of iron, the more massive elements can, in principle, be split into smaller pieces to get out some energy. This is nuclear fission. For practical purposes, the only fusion human beings can do at this time is heavier isotopes of hydrogen fused into helium releasing large amounts of energy. The only fission we can do is creating conditions where Uranium 233, Uranium 235, or Plutonium 239 atoms can spontaneously split, releasing energy for our purposes.

An exploding star going supernova sent a shock wave through a massive cloud of interstellar dust, left over from previous stars exploding. causing eddies that were swirling solar systems in the making. Most of the mass in this swirling cloud was concentrated at the center (called a protostar) and as the gravitational compression at the center became greater and greater as mass accreted, the core became dense and hot enough for the fusion of hydrogen into helium to begin. The sun was born. As long as the inward pressure from gravity balances the outward pressure from nuclear fusion in the core our sun will be a stable star. Earth and the other planets formed in the surrounding eddies orbiting the sun as static electricity first turned the dust into clumps and the lightning in the dust melted the clumps into rocks that collided to become planetesimals and eventually proto planets that smashed into each other until only five terrestrial planets remained in the inner solar system and the two gas giants and two ice giants were left in the outer solar system. One mars sized inner planet hit the Earth with a glancing blow that vaporized it and a good part of the upper mantle and crust producing a ring of hot debris that coalesced into the moon.

Radioactive decay is the natural process in which unstable nuclei emit ionizing radiation to eventually turn into stable non radioactive elements. Alpha particles are pieces consisting of two protons and two neutrons (essentially a helium nucleus), beta particles are electrons emitted when neutrons turn into protons while forming an electron and throwing it out so total charge remains the same. (Other things are conserved besides energy) Each radioactive element has its own pattern that is not affected by heat, chemical reactions or anything else outside the atom’s nucleus. The amount of time for half the original amount of material to change is called the “half-life”. In that amount of time half of the material will change. In that amount of time again half of what remains will change, and so in. It takes about TEN half lives for the starting amount of radioactive material to be one thousandth of the starting amount. It takes TWENTY half lives to drop to one millionth of the starting amount. The graph of material versus time is an exponential decay curve that can be used to predict remaining amounts at a given time or time to get to a particular amount. This makes it great for dating if you know how much material there was at the start. For example cosmic rays smash into oxygen and nitrogen atoms at the top of our atmosphere destroying them sending showers of protons and neutrons down into the lower atmosphere. If a neutron hits a nitrogen 14 nucleus and replaces the proton that it knocked out, you now have a carbon 14 atom. It is radioactive with a half life of 5700 years. When it goes through beta decay and a neutron becomes a proton turning it back into N14. Plants pull carbon from the air and put it in their bodies during photosynthesis. Animals eat plants etc. So living things have the same level of C14 in their bodies as is found naturally in the atmosphere. When they die, replacement stops. So comparing the C14 left in the body to the regular carbon in it one can calculate how long since it died. These are very small ratios so the method is not practical beyond 50,000 years or about ten half lives.

Using uranium to lead radioactive dating the age of the earth is Four and a half billion years.

The sun is one of the types of star that lives for about ten billion years. It is presently around five billion years old. As the hydrogen in the core gets used up as it is converted into helium. When the hydrogen is used up, the burned out core will collapse until it's hot enough to fuse helium into heavier elements such as carbon through iron. The new outward heat pressure will push the red outer layers out until it is a red giant. So about five billion years in the future, as the red giant stage ends, the outer gasses will expand away from the core leaving a dense hot white dwarf star that will cool by radiation over billions of years.

How do we know the behavior and history of stars since they live so much longer than human beings? Our telescopes let us observe stars near and far and we see them in all stages of their development. This is similar to a family photo album for human beings. It shows babies, young people, adults and old people. Also we use Newton’s and Kepler’s Laws on binary star orbits to determine their masses, we use their electromagnetic spectra to find out what elements are are in them and how fast they are moving and in what direction (the Doppler effect), and we apply the mathematics of nuclear fusion physics to figure out what is going on inside. It is all applied physics. The easiest way to visualize what is happening is with the Hertzsprung-Russell diagram which plots the brightness of stars on the vertical axis (from dimmest to brightest) and the temperature of stars (from hottest to coldest) on the horizontal axis. Stars start out as protostars that begin fusion at their cores when they get massive enough. They become adult stars whose temperature, brightness and lifetimes are determined by their initial mass. A star that is less than eight times the mass of the sun will go through its adult main sequence stage and end as a white dwarf star. A star that is between eight and twenty times the mass of the sun will end with a supernova explosion (creating many of the elements heavier than helium and through carbon) blowing all the outer layers into space leaving a neutron star behind in the middle. A star that is more than twenty times the mass of the sun will experience a supernova explosion leaving a black hole behind.

In the early twentieth century Hubble observed that the spectra of hydrogen and helium from stars in nearby galaxies were slightly longer wavelengths than found in a lab. The farther away the galaxies were in all directions from use the worse it got. Waves generated by a source moving away from an observer get slightly longer. The shift can be used to calculate the speed of motion. Hubble had found that all galaxies were moving away from us and the farther away they were the faster they were going. Either we were the center of the universe (unlikely) or the universe was expanding similar to bread dough full of raisins expanding before it gets baked. From the standpoint of any raisin, the others will be moving away and the farther away they are the faster they will be moving. Fred Hoyle, an astronomer who did not support the expanding universe model, coined the term “Big Bang” during a talk in 1949 to help the general audience visualize the model he was attacking. The name stuck. The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature to what it is now.