Physics: Derivations, Proofs and Experiments

Do not you think that a math formula is right or do you doubt any statement of a theory? Here you can eliminate your scientific doubt by formal reasoning (mathematical proofs, derivations) or empirical reasoning (experiments, studies).
Derivation
Level 3 (with higher mathematics)

Hall Voltage due to the Hall Effect

Derivation of the Hall voltage (via Hall effect), which depends only on quantities that we can easily determine in an experiment.

Derivation
Level 2 (without higher mathematics)

Electric Power

Simple derivation of the electric power P, which we express with voltage U and current I and then rewrite using the URI formula.

Derivation
Level 2 (without higher mathematics)

Head-on Elastic Collision and its 4 Special Cases

Derivation of the velocity formula for the elastic head-on collision of two different masses using conservation of momentum and conservation of energy.

Derivation
Level 2 (without higher mathematics)

Phase Velocity of a Wave

A simple derivation of the phase velocity of a wave from the definition of the wavelength and the period.