Unit 4 - Physics - Special Relativity

Einstein's Postulates of Special Relativity

- the laws of physics are the same in all inertial (non-accelerated) frames of reference. There is no absolute frame of reference. No law of physics can identify a state of absolute rest.
- the speed of light has a constant value for all observers regardless of their motion or the motion of the source

Spacetime

the concepts of time and three-dimensional space regarded as fused in a four-dimensional continuum.

The Twin Paradox

Important to read, on page 322 to 323 in Pearson Physics 12

Proper Time

time taken for event to occur in rest frame (same frame as when the observer of an event is at rest relative to the event). dilated time is always bigger then proper time. the clock shouldn't be moved.

4 consequences of Einstein's postulates

- time dilation
- length contraction
- mass-energy equivalence
- simultaneity

Proper Length

the length measured in the frame of reference in which the object is at rest. Person at rest measures proper length.

Mass-Energy Equivalence

as Kinetic energy is added to an object, its mass increases. Hence, mass can be seen as a form of energy (so that energy is conserved). At low speeds, more energy added is converted to speed. At high speeds, more energy added is converted to more mass.

Evidence of Mass-Energy Equivalence

- binding energy of nuclei
- fission and fusion
- annihilation of matter and antimatter
- production of matter from energy

Annihilation of matter

the process where positrons collide with electrons, destroying the two particles but producing gamma rays. Energy is released and mass is lost.

Production of matter from energy

- waves can produce matter from energy of waves.