Remember when you learned all about the basic structure of the atom – protons, neutrons, electrons? You might recall there was a lot of empty space, and you’d be right. Most of atoms is just empty space, so much so that if you gathered the entire human race together and removed the empty space of all the atoms that make them up you would be left with something no larger than a sugar cube. Incidentally…
Mechanics
- Weight (force of gravity) decreases as you move away from the earth by distance squared.
- Mass and inertia are the same thing.
- Constant velocity and zero velocity means the net force is zero and acceleration is zero.
Energy
- Mechanical energy is the sum of the potential and kinetic energy.
- Units: a = [m/sec2], F = [kg•m/sec2] (newton), work = pe= ke = [kg•m2/sec2] (joule)
- An ev is an energy unit equal to 1.6 x 10-19 joules
Electricity
- A coulomb is charge, an amp is current [coulomb/sec] and a volt is potential difference [joule/coulomb].
- Short fat cold wires make the best conductors.
- Electrons and protons have equal amounts of charge (1.6 x 10-19 coulombs each).
Magnetism
- The direction of a magnetic field is defined by the direction a compass needle points.
- Magnetic fields point from the north to the south outside the magnet and south to north inside the magnet.
- Magnetic flux is measured in webers.
Wave Phenomena
- Sound waves are longitudinal and mechanical.
- Light slows down, bends toward the normal and has a shorter wavelength when it enters a higher (n) value medium.
- All angles in wave theory problems are measured to the normal.
Geometric Optics
- Real images are always inverted.
- Virtual images are always upright.
- Diverging lens (concave) produce only small virtual images.
- Light rays bend away from the normal as they gain speed and a longer wavelength by entering a slower (n) medium {frequency remains constant}.
- The focal length of a converging lens (convex) is shorter with a higher (n) value lens or if blue light replaces red.
Modern Physics
- The particle behavior of light is proven by the photoelectric effect.
- A photon is a particle of light {wave packet}.
- Large objects have very short wavelengths when moving and thus can not be observed behaving as a wave. (DeBroglie Waves)
Internal Energy
- Internal energy is the sum of temperature (ke) and phase (pe) conditions.
- Steam and liquid water molecules at 100 degrees have equal kinetic energies.
- Degrees Kelvin (absolute temp.) Is equal to zero (0) degrees Celsius.
Nuclear Physics
- Alpha particles are the same as helium nuclei and have the symbol
- The atomic number is equal to the number of protons (2 for alpha)
- Deuterium (
) is an isotope of hydrogen (
)
MOST IMPORTANT FACTS
- The most important formulas in the physics regents are:
- Physics is Fun (HONEST)!