An object weights 10 N in air, 8 N in water. The buoyant force is MCQ with Answer and Explanation

Explanation:
Nucleus: protons (+) and neutrons (neutral); electrons orbit outside. Atomic number = proton count; mass number = protons + neutrons. Memory tip: 'Nucleus = nucleons (p+n); electrons in shells'. Basic atomic structure frequently tested in competitive modern physics sections.

Explanation:
g decreases with depth: g' = g(1 - d/R). At centre d=R, g'=0. Weightless at centre. At poles g=9.83, equator 9.78. At surface it's maximum.

Explanation:
Beats (periodic amplitude variation from interference of close frequencies) are used to tune instruments: adjust until beats disappear (frequencies match). Also, in Kundt's tube or other methods, beat frequency helps measure sound speed by comparing known and unknown frequencies. Memory tip: 'Beats: tuning (zero beat = matched frequency); speed measurement (beat frequency = |f₁-f₂|)'. This application question tests wave phenomena uses, frequently appearing in competitive exams. Always link physical phenomena to practical applications; competitive exams emphasize real-world relevance of physics concepts.