SONAR is based on the principle of: MCQ with Answer and Explanation

Explanation:
Mass m = 20 g = 0.02 kg. Momentum p = m v = 0.02 × 200 = 4 kg m/s. Always convert mass to kg. Momentum unit kg·m/s.

Explanation:
Spring-mass period T = 2π√(m/k), depending only on mass and spring constant, not on gravity. In orbit, apparent weightlessness doesn't affect spring force (which depends on displacement, not gravity). Thus period remains unchanged. Pendulum period would change (depends on g), but spring-mass does not. Memory aid: 'Spring period: independent of g; pendulum period: depends on g'. This conceptual question tests oscillations fundamentals, frequently examined in competitive exams. Always distinguish gravity-dependent (pendulum) from gravity-independent (spring-mass) oscillators.

Explanation:
Linear expansion formula: ΔL = L₀αΔT, where ΔT = T - T₀. Thus new length L' = L₀ + ΔL = L₀[1 + α(T - T₀)]. Option A incorrectly uses absolute temperature T instead of temperature change. Option C gives only the change, not total length. Option D uses initial temperature incorrectly. Memory aid: 'Expansion depends on temperature change, not absolute value'. This standard formula application is common in thermal physics questions. Always identify initial length and temperature reference point to avoid sign errors.