A gun recoils on firing because of MCQ with Answer and Explanation

Explanation:
For an ideal gas, internal energy U depends solely on temperature (U = f/2 nRT, where f is degrees of freedom). This follows from kinetic theory: no intermolecular forces, so energy is purely kinetic, proportional to T. Pressure and volume can change at constant T (isothermal process) without changing U. Memory tip: 'Ideal gas: U = U(T) only; real gases have volume dependence'. This thermodynamics concept is frequently tested in competitive exams. Always distinguish ideal vs real gas behavior; competitive exams typically assume ideal gas unless specified.

Explanation:
Light speed max in vacuum c = 3×10⁸ m/s. Slower in medium, v = c/n. Higher n, slower. Diamond n≈2.42, speed lowest. Vacuum n=1.

Explanation:
Sound travels to cliff and back. Total distance = speed × time = 340 × 2 = 680 m. So distance to cliff = 680/2 = 340 m. Use formula d = (v × t)/2. Time for round trip. Minimum distance for echo 17 m (approx) for 0.1 s persistence.