Moderator (water, graphite) slows fast neutrons to thermal energies for efficient fission in U-235. Control rods absorb neutrons to regulate reaction. Memory tip: 'Moderator = neutron slower; Control rods = neutron absorber'. Reactor component function frequently tested in competitive nuclear physics questions.
Explanation:
Thomas Alva Edison invented the practical incandescent light bulb in 1879. He also invented phonograph. Tesla contributed to AC system. Faraday electromagnetic induction. Bell telephone.
The escape velocity from Earth's surface is approximately 11.2 km/s. If a planet has twice Earth's radius and same density, its escape velocity will be:
Explanation:
Escape velocity v_e = √(2GM/R). Mass M = density ρ × volume = ρ×(4/3)πR³. Thus v_e = √(2Gρ×4/3πR³ / R) = √(8GρπR²/3) ∝ R√ρ. Given same density and R_planet = 2R_earth, v_e ∝ R, so v_e_planet = 2 × 11.2 = 22.4 km/s. This derivation shows escape velocity scales linearly with radius for constant density. Memory tip: v_e ∝ √(M/R) and M ∝ R³ for constant ρ, so v_e ∝ R. Such proportional reasoning questions test conceptual grasp of gravitation formulas in competitive exams without heavy calculation.
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