CONGRATULATIONS!

For any 2010 seniors who might be reading this for some reason: we are DONE with Physics!!! I hope it was helpful! I don't really know what to do with this thing now, but I guess if future classes of Physics students really want to use this as a resource, they're welcome to!

Paper 3 Review

The outcome of a star depends on the star's initial mass (in terms of solar masses).

• <0.25
• 0.25 - 4 White dwarf with carbon/oxygen core
• 4 - 8 White dwarf with oxygen/neon/magnesium core
• 8 - 40 Neutron star
• >40 Black hole

Fg = GMm/r^2

b = L/4πd^2 units: W/m^2

The Schwarzschild radius is the distance from the center of a black hole within which no light is able to escape.

Relativity Notes

Michelson-Morley Experiment:

• The purpose of the experiment was to determine the nature of light, and whether there was an aether.
  
• A change in the interference pattern was expected.
• No change in the interference pattern was actually observed.
• The speed of light along the path from mirror M1 to the semi-transparent mirror is c - v, when c is the speed of light and v is the orbital speed of Earth.

The proper time of something in a frame of reference is the time measured from within that frame of reference.

Remember that you can relate mass to energy using E = mc^2

Also remember:

• v = f λ
• c = f λ
• f = c/λ
• Eγ = hf = hc/λ

Evidence for Black Holes

There is a force holding stars in orbit:

1. at the center of the galaxy
2. within a binary system

The emission of x-rays as charged particles are accelerated toward the event horizon.

Greenhouse Gases

Greenhouse gases, like methane and carbon dioxide, absorb infrared radiation and turn it into thermal energy, making the world warmer.

Gravitational Field!

UNITS ARE IMPORTANT!

Gravitational field is referring to Force per unit Mass, which is the acceleration of gravity!

This is because the units for F/m are Newtons per kilogram. Newtons are equal to kilogram meters per second squared, so the units cancel out to become the unit for acceleration: meters per second squared.

Electricity and Magnetism Notes (In Progress)

There are two kinds of charge: positive and negative.

Electric charge is conserved. It cannot be created or conserved.

The total charge of the universe is believed to be zero (there is exactly as much positive charge as negative).

Methods of charging:

• Charging by Friction: When two objects are rubbed together, frictional forces remove electrons from one object and give them to the other object. The object that loses electrons may develop a positive charge, while the one that gains electrons may become negative.
• Charging by Induction: An object gains a charge without actually making contact with another charged object. For example, a negatively charged rod may repel electrons from a nearby conductor. The electrons from the conductor would flow into the earth, leaving the conductor positively charged.
  

IB Physics Wikibook

I haven't spent much time looking at it myself, but this online study guide might be helpful:
http://en.wikibooks.org/wiki/IB_Physics

Mock Review: Units

Fundamental Units:

Mass: Kilogram (kg)

Length: Meter (m)

Time: Second (s)

Electric Current: Ampere (A)

Amount of Substance: Mole (mol)

Temperature: Kelvin (K)

Luminous intensity: Candela (cd)

Derived Units: Note: x^-1 = 1/x and x^-2 = 1/(x²)

Newton (N) = kg m s^-2

Pascal (Pa) = kg m^-1 s^-2

Hertz (Hz) = s^-1

Joule (J) = kg m² s^-2

Watt (W) = kg m² s^-3

Coulomb (C) = A s

Volt (V) = kg m² s^-3 A^-1

Ohm (Ω) = kg m² s^-3 A^-2

Weber (Wb) = kg m² s^-2 A^-1

Tesla (T) = kg s^-2 A^-1

Becquerel (Bq) = s^-1

Gray (Gy) = m² s^-2

Sievert (Sv) = m² s^-2

Mock Exam Review Notes

Accurate: The measured value is close to the true value (small systematic error), but are not necessarily precise

Precise: Repeated measurements have the same value (small random error), but are not necessarily accurate. Precision can be improved by repeating the experiment.

Equilibrium (ΣF = 0): When an object is in equilibrium, the sum of the forces acting on it is zero.

Terminal Velocity: The maximum velocity of a falling object

Newton's Laws of Motion:

1. Unless acted on by an external force, moving objects will remain in uniform motion in a straight line, and objects at rest will stay at rest. External forces cause acceleration.
   
2. Force = mass x acceleration or F = m a
3. For every action, there is an equal but opposite reaction. (Example: If a person pushes against a wall, the wall pushes back with the same amount of force)

Newton's Law of Universal Gravitation:

• Every object in the universe attracts every other object in the universe. This attraction is only significant if the objects involved are massive.
• Universal Gravitational Constant (G) = 6.67 x 10^-11 Nm² kg^-2

Gravitational Field Strength:

• g = F/m
• g = (G M)/r² where M is the mass of the planet
  

Conservation of Momentum: The momentum (p) of a system will remain constant unless the system is acted on by an outside force. Remember: the formula for momentum is p = m v

Escape Speed: The speed needed for an object to escape the gravitational attraction of a planet. Can be found with the formula v = √( (2 G M)/R) where R is the radius of the planet.

Conservation of Energy: Energy is not created or destroyed, it just changes its form

Centripetal Acceleration: a = v²/r

Centripetal Force: F = m a = mv²/r

Celsius to Kelvin Conversion: 0 degrees C = 273 K

Thermal Capacity: The energy required to raise an object's temperature by 1 K

• C = Q/∆T, where C is an object, Q is a quantity of thermal energy, and ∆T is the change in temperature
  

Specific Heat Capacity: The energy required to raise a unit mass of a substance by 1 K

• c = Q/(m∆T)
  

Specific Latent Heat (L): The amount of energy per unit mass absorbed or released during a change of phase

• L = Q/m
• Q = mL

Laws of Thermodynamics:

1. ∆U = ∆Q + ∆W, where ∆U is the change in the internal energy of a system, ∆Q is the thermal energy, and ∆W is the work done. If ∆Q is positive, the thermal energy of the system is increasing. If it is negative, the thermal energy is decreasing. Similarly, if ∆U is positive the internal energy of the system is increasing, and if it is negative the internal energy is decreasing. If ∆W if positive, the system is doing work on its surroundings, while if it is negative the surroundings are doing work on the system.
2. No heat engine can take in heat from its surroundings and convert it totally into work. The entropy of the universe can never decrease.

Ideal Gas Processes:

• Isothermal: the gas has a constant temperature
• Isobaric: the gas has a constant pressure
• Isochoric (isovolumetric): the gas has a constant volume
• Adiabatic: there is no thermal energy transfer between the gas and its surroundings. If the gas does work it must result in a decrease in internal energy.
  

For ideal gases, PV = nRT, where:

• P is pressure
• V is volume
• n is the amount of gas (the units are moles)
• R is the molar gas constant (R = 8.314)
• T is the temperature
  

Simple Harmonic Motion: When an object moves back and forth from a fixed average point (the mean position).

Diffraction: When waves go through openings, they usually spread out. They also spread around obstacles.

Coulomb's Law: F = (k q₁ q₂) / r² where:

• F is the force between two point charges
• k is the Coulomb constant
• q₁ and q₂ are the point charges
• r is the distance between the point charges
  

Mock Exam Review

Notes covering the topics on the mock exam review sheet are on the way!

Hertzsprung Russell Diagram

Pretty good HR Diagram I found online. Click on it to make it bigger.

Class Notes 3/25

Newton's Universe:

1. Infinite size
2. Infinite number of stars
3. Infinite age
4. Homogeneous distribution of stars

H-R Diagram:

• X-Axis: Temperature in K (Note: increases from right to left)
• Y-Axis: Luminosity in Watts
• Main Sequence: made up of dwarf stars (mostly red dwarfs)
• White Dwarfs: below the main sequence, near the lower left corner of the graph
• Cepheid Variables: near the center of the graph, slightly above the main sequence
  

Wolfram Alpha

This website is great for Physics:

www.wolframalpha.com

It seems like you can type in basically any physics concept or formula and it will tell you all about it and answer your math questions. It can do some pretty complicated stuff, and it will convert units if you want it to. I think this could be very helpful.

Class Notes 3/23

Olber's Paradox

1. Newtonian idea of the universe assumes infinite universe and infinite number of stars with homogeneous distribution
2. Number of stars of distance d is about d^2
3. L = b/(4πd^2)

Hubble

1. Discovered galaxies and the enormous number of them
2. The further away a galaxy was the more the Hydrogen spectrum was shifted toward the red.
3. v = H0(d) where H0 is called Hubble's constant
4. (∆λ) / (λref) = v/c
5. The universe is expanding leading to the Big Bang cosmology.
6. Ho = 2.2 x 10^4 m/sMly
7. From v = H0(d) and d = v(avg)T:
   T = d/v(avg) = 1/H0

Schwarzchild Radius:

R = (2GM) / (c^2)

More Astrophysics Notes

What determines the brightness of a star?

• b = L / (4πd²) [W/m²]

What determines the luminosity of a star?

• Assuming a blackbody radiator:

o L = σAT⁴

o σ = 5.67 x 10^-8 [W/m²K⁴]

What determines the surface temperature of a star?

• Wein's Law: T = (2.90 x 10^-3(K·m))/ (λ_max)

More massive stars are also more luminous.

Absolute magnitude (M) is the magnitude of a star when observed from 10 parsecs.

Relative magnitude (m) is the magnitude of a star when observed from the Earth (or nearby).

Stars radiate energy through hydrogen fusion.

F_g = GMm/d²

White dwarf- in equilibrium (not a black hole) due to "electron degeneracy"

1 parsec = 3.26 light-years

Astrophysics Notes

How is the Universe Organized?

· The force of gravity clusters matter at an astronomical scale.

· Clusters within the universe

o Solar Systems consist of: one or more stellar bodies, planets, moons, asteroids, comets, dwarf planets (e.g. Pluto, Eris), Kuiper-belt like debris

o Stellar clusters consist of solar systems

o Galaxies

o Galactic clusters consist of galaxies

· Stars and planets are different because stars emit light while planets reflect light.

· A light-year (ly) is the distance light travels in a year.

· 1 ly = (2.998 x 10⁸ m/s) (3.156 x 10⁷ s/yr) = 9.46 x 10¹⁵ m ≈ 10¹³ km

· Our galaxy is 100,000 ly wide, 2,000 ly tall

· Wein's Law for a blackbody radiator: λ_max = (2.90 x 10^-3) / T (kelvin)

· Gravity bends light

· Andromeda is 2 million ly away

Nuclear Physics Vocabulary

Nuclear Reaction- Occurs when a nucleus is struck by another nucleus or particle. Energy and momentum must be conserved. Neutrons are very effective in nuclear reactions because they have no charge and therefore are not repelled by the nucleus. A generic reaction follows the formula of

a+X —> Y+b

Transmutation- When the original nucleus in a nuclear reaction is transformed into another. Can be natural or artificial.

Moderator- Needed to slow neutrons so that their probability of interacting increases. Common moderators are heavy water and graphite.

Critical Mass- The mass below which a chain reaction will not occur because too many neutrons escape.

Control Rods- Parts of nuclear reactors (usually cadmium or boron) that absorb neutrons and are used for fine control of reactions, keeping them just barely critical.

Nuclear Fusion- The lightest nuclei can fuse to form heavier nuclei, releasing energy in the process.

Becquerel (Bq)- The SI unit for activity

Dosimetry- The measurement of radiation