Thursday, April 29, 2010

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

Wednesday, April 28, 2010

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.

Monday, April 26, 2010

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.

Wednesday, April 7, 2010

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

Sunday, April 4, 2010

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