A radioactive substance decays to 1/16th of its original mass in 20 days. Half-life is MCQ with Answer and Explanation

Explanation:
Binding energy per nucleon peaks around iron-56 (≈8.8 MeV/nucleon), making it the most stable nucleus. Lighter nuclei release energy via fusion; heavier via fission. Hydrogen has near-zero binding energy per nucleon; uranium ≈7.6 MeV/nucleon. Memory aid: 'Iron peak: most stable nucleus; fusion before, fission after'. This nuclear physics concept is frequently tested in competitive exams. Always link binding energy curve to energy release in stars (fusion) and reactors (fission).

Explanation:
Each part resistance = R/3. Three such in parallel: 1/R_eq = 3/(R/3) = 9/R => R_eq = R/9. For n equal parts cut and connected parallel, R_eq = R/n².

Explanation:
In the SI system of prefixes, 'Peta' stands for 10^15. Other common large prefixes include Kilo (10^3), Mega (10^6), Giga (10^9), Tera (10^12), and Exa (10^18). It's crucial to memorize both positive and negative powers (like nano, pico, femto) for competitive exams.