The centre of mass of a uniform semicircular ring of radius R lies at distance from centre MCQ with Answer and Explanation

Explanation:
Protium (¹H), Deuterium (²H), Tritium (³H) are all isotopes of hydrogen, differing in neutron number.

Explanation:
Potential difference V = W/q: work per unit charge. Electric field E = F/q: force per unit charge. Memory tip: 'Potential = work/charge (scalar); Field = force/charge (vector)'. Electrostatics definition frequently tested in competitive exams.

Explanation:
Einstein explained photoelectric effect (1905) using light quanta (photons), earning Nobel Prize. Also developed relativity. Electron: Thomson; Nuclear atom: Rutherford; Induction: Faraday. Memory aid: 'Einstein = photons + relativity'. Key contribution frequently tested in competitive modern physics history questions.