# Special Relativity test

1. Sep 22, 2009

### awri

Today I have a test on sp. relativity. This subject is quite different for the other physics courses and thus I am unsure what to focus on. What are the most common types of questions asked about sp. relativity? Whats most important?

2. Sep 22, 2009

### turin

That depends on your syllabus. Indeed, approaches to Special Relativity are quite varied, and can depend on, e.g., what you are using it for.

I try to understand SR in terms of representations (such as scalars, vectors, tensors, and how to write Lorentz transforms in matrix form) and invariants (such as the speed of light, contractions, and the metric tensor). Then, how are these things physically interpretted.

Depending on how complex and involved your course is, think about:
- metric (tensor): proper length/time, contraction, raising and lowering indices, invariance of
- Lorentz transform: matrix representation, system of equations, gamma and beta, raptidity, pseudo-rapidity, rotations vs. boosts, decomposition into a rotation and a boost, "2x2 matrix" representation (Pauli matrices or quaternions)
- the distinction between: proper time and coordinate time, rest mass and "relativistic mass", proper velocity and coordinate velocity

Some specific issues/applications that could appear:
- resolving the twin paradox (and variaous other paradoxes)
- elegant formulation of electromagnetism: 4-current density, Faraday tensor, Levi-Civita tensor (I would argue that this is of particular importance/relevance to SR, and you should focus on this regardless of what's on the exam.)
- timing and stability in particle accelerators
- kinematical distributions (e.g. in angle, energy, invariant mass, etc.)

Last edited: Sep 22, 2009
3. Sep 22, 2009

### awri

Well some of the things you said were on there. The metric tensor definitely, lots of rotations and other cross product infused techniques (yuck). I dont know what the twin paradox is though. Thanks for your help btw